The Hammers produced an emphatic second-leg comeback over Freiburg to reach the last eight, while Xabi Alonso's men eliminated Azerbaijani hopefuls Qarabag in the most incredible circumstances.
Match preview
With 41 games done and dusted in the 2023-24 campaign, Bayer Leverkusen have extraordinarily managed to avoid defeat in every single one of them, although their glorious sequence was on the cusp of being broken by Qarabag in an unforgettable last-16 encounter.
After returning from the long trip to Azerbaijan with a creditable 2-2 draw under their belts, Alonso's crop stared elimination in the face as Qarabag took a 2-0 second-half lead at the BayArena, but Jeremie Frimpong's strike and an incredible injury-time brace from Patrik Schick completed the mother of all turnarounds.
That sensational 3-2 success represents the second victory of an ongoing six-match winning run for Thursday's ostensibly unstoppable hosts, who have a DFB-Pokal final with Kaiserslautern to look forward to on May 25, and just one more three-point haul will end Bayern Munich's 11-year reign of Bundesliga supremacy.
As Leverkusen edged past Union Berlin 1-0 at the weekend thanks to Florian Wirtz penalty, Alonso's former team suffered a chastening 3-2 loss to Heidenheim, leaving Die Werkself 16 points clear of Bayern and Stuttgart at the Bundesliga summit with only 18 left to fight for.
Sunday's home clash with Werder Bremen could therefore act as Leverkusen's coronation party, but before domestic celebrations can commence, Alonso's men have a Europa League record to match; they have won all four of their home games in the 2023-24 edition while scoring at least three goals each time, and only Chelsea did so five times in a row in 2018-19.
With the Blues going all the way to continental glory that year, the omens are highly promising for Leverkusen should they manage to replicate the feats of their counterparts from the Premier League, where Liverpool-linked Alonso will not be ending up this year on account of his decision to continue in the BayArena hotseat.
Upcoming foes West Ham have already experienced one frustrating result on German shores in 2024, going down 1-0 to Freiburg in their opening last-16 tie after having a last-gasp penalty appeal waved away, but David Moyes's men righted those wrongs in style with a 5-0 second-leg slaughter.
Slowly building up their continental pedigree, the Europa Conference League holders have now made the quarter-finals in each of their last three appearances in European competition and are yet to suffer last-eight heartbreak, smashing Lyon 4-1 at this stage in the 2021-22 Europa League before German-inflicted semi-final misery versus Eintracht Frankfurt.
The Irons only took two points from the three Premier League games that immediately followed their five-goal romping of Freiburg - throwing away a 3-1 lead to Newcastle United in that sequence - but they returned to victorious ways at the weekend, eking out a 2-1 win over Wolverhampton Wanderers thanks to James Ward-Prowse's goal direct from a corner.
Thursday's contest will mark the first time that Leverkusen and West Ham have squared off in a competitive setting, but the Bundesliga leaders demolished the Irons 4-0 during a pre-season friendly back in August, and a similar result in the first leg of their quarter-final would all but eradicate the visitors' ambitions of back-to-back continental crowns.
Bayer Leverkusen Europa League form:
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Bayer Leverkusen form (all competitions):
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West Ham United Europa League form:
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West Ham United form (all competitions):
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Team News
Leverkusen's narrow success over Union Berlin at the weekend was far from the perfect afternoon for Alonso, who lost promising Czech attacker Adam Hlozek to a first-half ankle injury, while Nathan Tella also had to come off in the second period with a hip issue.
Hlozek is expected to miss a few weeks with his problem - ruling him out of both legs of the quarter-final - and while the severity of Tella's problem is still unknown, the dangerous Frimpong should displace the ex-Southampton man either way. Brazilian Arthur is another option on that side, but he is doubtful due to fitness reasons.
Hlozek's injury is not so debilitating for Leverkusen thanks to the availability of Schick and Victor Boniface - who made his first appearance since December on Saturday following a severe adductor problem - but the Nigerian may not be deemed ready for a starting place just yet.
Moyes can empathise with Alonso when it comes to fresh attacking fitness woes, although West Ham's is much more worrisome, as Jarrod Bowen was forced off early in the second half of the Irons' triumph over Wolves with what is believed to be 'severe' spinal bruising.
West Ham fans are anxiously awaiting official updates on the Englishman's condition, but his chances of an appearance on Thursday evening are not looking strong, while Alphonse Areola is definitely absent as he recuperates from a groin problem, and Edson Alvarez is suspended.
Kalvin Phillips would be a like-for-like replacement for Alvarez, but the Manchester City loanee has endured a disastrous start to life at West Ham, so Moyes may elect to switch to a three-man backline instead.
Bowen's likely absence will likely lead to a straight swap with Antonio at the focal point of the Hammers' attack, while Czech teammates Vladimir Coufal and Tomas Soucek should reprise their roles, despite both coming off at the break at Molineux.
Bayer Leverkusen possible starting lineup:
Hradecky; Kossounou, Tah, Hincapie; Frimpong, Xhaka, Andrich, Grimaldo; Wirtz, Adli; Schick
West Ham United possible starting lineup:
Fabianski; Coufal, Zouma, Mavropanos; Johnson, Soucek, Ward-Prowse, Emerson; Kudus, Paqueta; Antonio
We say: Bayer Leverkusen 2-0 West Ham United
No Bowen does not necessarily mean no party for West Ham fans, who rejoiced in seeing Mohammed Kudus run Freiburg ragged in the last 16, but an unbeaten and unwavering Leverkusen side are a different kettle of fish entirely.