A record 40 teams split into 10 groups will take part in the 2021 AFC Champions League as the competition continues to go from strength to strength, showcasing Asia's finest teams and numerous world-renowned players.
Having so far looked at the tournament over its first 15 years, we shift the focus to the more recent editions, when there was glory for a trio of powerhouses from Japan, Saudi Arabia and Korea Republic.
2018 AFC Champions League: Kashima join the roll of honour
Defending champions Urawa Red Diamonds failed to qualify for the 2018 edition but former winners Al Ain, Al Sadd, Guangzhou Evergrande, Jeonbuk Hyundai Motors and Ulsan Hyundai were all present, and all five successfully navigated the group stage into the knockout rounds.
Elsewhere in the West, Al Duhail were on fine form, winning all six of their games to advance to the next round, while Tehran giants Persepolis and Esteghlal won their respective groups. Al Hilal, meanwhile, were the biggest casualty as the 2017 runners-up were eliminated without picking up a single victory.
On the other side of the continent, Japan's Kashima Antlers progressed despite winning just two of their six games, while Chinese debutants Tianjin Quanjian and Thailand's Buriram United – who reached the last 16 for just the second time – were among the teams to progress.
Iranian and Qatari clubs shone in the last 16 as Persepolis struck at the death to eliminate Al Jazira and Esteghlal saw off domestic rivals Zobahan. Al Duhail stretched their winning run to eight with back-to-back victories over Al Ain and a Baghdad Bounedjah second-leg brace was enough for Al Sadd to defeat Al Ahli Saudi.
Kashima edged past Shanghai SIPG with Shoma Doi's away goal proving decisive, while former champions Guangzhou and Ulsan were eliminated by their domestic rivals Tianjin and Suwon Samsung Bluewings respectively. Two-time winners Jeonbuk, though, had too much for Buriram over two legs.
Al Duhail made it nine wins in a row to match Ulsan's achievement from 2012 after a quarter-final first-leg win over Persepolis, only for a 3-1 second-leg defeat to confirm their exit. Their countrymen Al Sadd, however, had more joy against Tehran opposition, Bounedjah scoring three over two legs to secure a place in the semi-finals.
By now Go Oiwa's Kashima were beginning to find their rhythm as they eased past Tianjin 5-0 on aggregate, with new signing Serginho scoring a goal in each leg. After winning 3-0 in Jeonju, meanwhile, Suwon lost to Jeonbuk by the same scoreline at home only to scrape through to the last four on penalties.
Persepolis claimed a 1-0 away win against Al Sadd in the first leg of the semi-finals but were made to sweat in front of a packed Azadi Stadium in the return meeting. With the score at 1-1 and the Doha side needing just a goal to advance, Alireza Beiranvand produced a world-class save to deny Xavi Hernandez from close range as Branko Ivankovic's team progressed to the final for the first time.
A late Atsuto Uchida goal had sealed a 3-2 first-leg victory for Kashima over Suwon in the other semi-final but Suwon fought back to lead 3-2 in the second leg. With the game on a knife edge, Serginho swivelled and fired home in the final 10 minutes to secure a topsy-turvy 6-5 aggregate win.
Kashima Soccer Stadium played host to the first leg of the final and the home fans were treated to a comfortable victory as Brazilian duo Leo Silva and Serginho netted in a 2-0 win, while Persepolis' misery was compounded when Siamak Nemati was dismissed in the closing stages.
Some 100,000 spectators turned up at the Azadi a week later, hoping to inspire another famous victory, but the hosts were unable to break down a stubborn Kashima backline. Oiwa's men held out for a goalless draw and with it claimed Asia's most prestigious club title for the first time as the trophy remained in Japan for the second successive year.
2019 AFC Champions League: Al Hilal finally triumph
Kashima's defence of their title got off to a winning start as they defeated Malaysian debutants Johor Darul Ta'zim 2-1 before eventually advancing to the Round of 16, while six other former winners – Al Ittihad, Al Sadd, Guangzhou, Jeonbuk, Ulsan and Urawa – also booked their passage into the next phase.
Al Zawraa hosted the first AFC Champions League to ever be played in Iraq, and dealt Al Wasl a comprehensive 5-0 defeat, although ultimately fell at the first hurdle, as did inaugural champions Al Ain and Tehran duo Esteghlal and Persepolis. In the East, J1 League champions Kawasaki Frontale were among the big names to suffer an early exit.
The last 16 pitted Al Hilal against domestic rivals Al Ahli Saudi and Bafetimbi Gomis proved the hero, with the Frenchman's first-leg hat-trick crucial in a 4-3 aggregate win. Fellow Saudi sides Al Ittihad and Al Nassr also reached the last eight after seeing off Al Wahda and Zobahan, while Al Sadd – now managed by Xavi – overcame city rivals Al Duhail.
A number of tight affairs in the East saw Kashima oust Sanfrecce Hiroshima on away goals, Guangzhou eliminate Shandong Luneng after extra time and Shanghai SIPG defeat Jeonbuk on penalties. The 2017 champions Urawa, meanwhile, reversed a 2-1 first-leg deficit to win 3-0 away at Ulsan and march on to the quarter-finals.
Al Hilal again faced Saudi opposition in the last eight and, after a goalless draw in the first leg against Al Ittihad, Salem Al Dawsari starred in a 3-1 win that saw the Riyadh giants come from a goal down to progress. A late Bounedjah penalty in Doha saw Al Sadd edge Al Nassr 4-3 over two legs.
Kashima's defence of their title came to an end in front of home support as Anderson Talisca's header was enough to take Guangzhou through on away goals. But Urawa returned to the semi-finals to fly the flag for Japan after also winning on away goals following their 3-3 aggregate draw against Shanghai SIPG in which Shinzo Koroki scored in both legs.
Gomis was again on form in the semi-finals as the striker scored twice – after initially netting at the wrong end – in a 4-1 win at Al Sadd that seemingly put Al Hilal well on their way to the final. But they were made to sweat in the return meeting before advancing 6-5 on aggregate following a 4-2 loss in Riyadh.
There were few such problems for Urawa, though, as goals from Fabricio and Takahiro Sekine secured a 2-0 first-leg win over Guangzhou before Koroki headed home at Tianhe Stadium to book a return to the showpiece event and ensure a repeat of the 2017 finale.
Al Hilal gave themselves real hope of claiming that elusive first AFC Champions League title after Andre Carrillo's second-half header at Riyadh's King Saud University Stadium saw them edge the first leg 1-0 and ensure they would travel to Japan having not conceded an away goal.
Two weeks later at Saitama Stadium, Razvan Lucescu's team were in no mood for a repeat of the 2017 final. Having been the better side throughout, Al Dawsari, who was sent off at the same venue two years earlier, put Al Hilal in front with a little over 15 minutes to play before Gomis wrapped up proceedings in stoppage time for a famous 3-0 aggregate win.
After suffering defeats in the 2014 final against Western Sydney Wanderers and to Urawa three years later, Al Hilal had finally won the trophy they craved most as they added to the six Asian club titles they had claimed over the years. For the first time in eight years, meanwhile, the AFC Champions League was won by a team from the West.
2020 AFC Champions League: Ulsan become two-time champions
As with every other AFC Champions League campaign, there was plenty of excitement ahead of the 2020 edition, with Andres Iniesta's competition debut among the biggest highlights. The Spanish FIFA World Cup winner starred in back-to-back wins for Vissel Kobe although the competition was brought to a halt after Sydney FC's 2-2 draw against Jeonbuk on March 4 due to the worsening COVID-19 situation.
Just over six months later, the sides from the West resumed action in the centralised venue of Qatar, where defending champions Al Hilal were forced to withdraw after a COVID-19 outbreak within their squad, although their domestic rivals Al Ahli Saudi, Al Nassr and Al Taawoun all made the last 16.
There was also a return to the knockout rounds for Persepolis and Esteghlal, Uzbekistan's Pakhtakor advanced for the first time since 2010 and the United Arab Emirates' Shabab Al Ahli Dubai made the cut too.
Abderrazak Hamdallah was on red-hot form for Al Nassr, with the Moroccan's goal seeing Al Nassr past Al Taawoun in the last 16, while Al Ahli Saudi edged Shabab Al Ahli on penalties. Persepolis, yet to concede from open play in Qatar, ousted Al Sadd after Isa Alkasir's late goal and Pakhtakor progressed by defeating Esteghlal 2-1.
Al Nassr then came out on top of another all-Saudi clash by easing past Al Ahli Saudi to advance to the semi-finals for the first time, and they would be joined by Persepolis after Yahya Golmohammadi's team recorded yet another clean sheet in a 2-0 win over Pakhtakor in which Alkasir added two more goals.
Hamdallah put Al Nassr in front from the spot in the semi-finals but Mehdi Abdi Qara levelled shortly before the interval and, with no further goals, the game was ultimately decided from the spot. Persepolis held their nerve, scoring five from five, to return to the final for the second time in three years.
Two months later the teams from the East arrived in Qatar and big names fell at the first hurdle as both Guangzhou and Jeonbuk were eliminated. But another former winner, Ulsan, were on superb form as they won five from five to progress, while J1 League trio Vissel, FC Tokyo and Yokohama F. Marinos, Chinese pair Beijing FC and Shanghai SIPG, Korea's Suwon and Australia's Melbourne Victory also advanced.
Iniesta was on the scoresheet to help Vissel past Shanghai and Ulsan's fantastic form continued as they beat Melbourne 3-0. Beijing secured a place in the last eight for the first time after they edged FC Tokyo while Suwon produced the result of the round by ousting the highly fancied Yokohama 3-2.
Junior Negrao then bagged a brace as Ulsan downed Beijing 2-0 to reach the semi-finals before Vissel and Suwon's 1-1 draw ensured their quarter-final would be decided from the spot. And it was the Kobe club who advanced after a 7-6 victory; however, it was not all good news as Iniesta aggravated an injury when taking his penalty and was ruled out for the tournament.
The semi-final was equally as dramatic with Vissel going in front through Hotaru Yamaguchi early in the second half before Bjorn Johnsen levelled with 10 minutes to play as the game went to extra time. Then, with penalties looming, Negrao netted from the spot to send Ulsan into the final for the first time since winning the competition in 2012.
Aiming to banish the ghost of the 2018 final, Persepolis went in front at Al Janoub Stadium when Abdi Qara struck as half-time approached, only for Negrao to level deep into first-half stoppage time when he sent home the rebound after initially seeing his penalty saved. Ten minutes after the interval, the Brazilian had another opportunity from the spot and this time he made no mistake to put Ulsan 2-1 up.
And that's how the score remained as the K League 1 side matched their 2012 record of nine straight wins to ensure the trophy returned to Korea Republic for the first time since Jeonbuk won it in 2016. It was further heartbreak for Persepolis, meanwhile, as they lost in the final for the second time in three years while Iran's long wait for an AFC Champions League title continues.