AC Milan and defending champions Barcelona are hot favourites to progress to the quarter-finals of the Champions League, but Arsenal are on the brink of elimination. Milan take a 4-0 lead to London on Tuesday evening, while Barcelona -- who got the better of the Italian champions in the group phase -- have a 3-1 advantage to defend when Bayer Leverkusen visit Camp Nou on Wednesday. A slickly taken first-half hat-trick from the returning Zlatan Ibrahimovic set Milan on the way to a 4-0 win at Palermo on Saturday that enabled them to open up a three-point lead over Juventus at the Serie A summit. Massimiliano Allegri\'s side were similarly ruthless in the first leg of their tie against Arsenal three weeks ago, when a Robinho brace helped the seven-time European champions condemn the Londoners to their heaviest defeat in continental competition. Arsene Wenger labelled his side\'s performance \"shocking\" and the Gunners must now do what only three teams have managed to do in the history of UEFA tournaments and overhaul a four-goal deficit from the first leg of a knockout tie. Milan, however, have unwanted experience of throwing away handsome leads in the Champions League. In 2003-04, they went out to Deportivo La Coruna in the quarter-finals despite leading 4-1 from the first leg and the following season witnessed their famous loss on penalties to Liverpool in the final after they went in 3-0 up at half-time. Arsenal can also take heart from a run of four straight wins in the Premier League, the latest a smash-and-grab 2-1 success at Liverpool on Saturday that took them to within four points of third-placed Tottenham Hotspur. Six of Arsenal\'s last 19 home wins in Europe have been by four goals or more, and Wenger knows that in Robin van Persie -- scorer of both goals at Anfield -- he possesses one of Europe\'s most in-form strikers. \"We will give absolutely everything to win,\" he told the Arsenal website. \"We know the statistics are against us, but you can realise the impossible when you don\'t know it is impossible. Let\'s ignore that and just go for it.\" Leverkusen face a similarly daunting task against a Barcelona side who appear to have rediscovered themselves in recent weeks, having registered three consecutive wins culminating in Saturday\'s 3-1 success over Sporting Gijon in La Liga. Furthermore, Pep Guardiola\'s side are unbeaten in 13 European home games and Leverkusen have not won away from home in Europe\'s premier club competition for more than a decade. Barca will welcome back tournament top scorer Lionel Messi after he missed the victory over Gijon through suspension, but forward Alexis Sanchez (thigh) and left-back Eric Abidal (groin) are both likely to miss the game due to injury. Perhaps the most finely poised match of the week sees Zenit Saint-Petersburg travel to Benfica on Tuesday protecting a 3-2 lead from the first leg. Roman Shirokov\'s 88th-minute winner gave Zenit victory at Stadion Petrovski on Valentine\'s Day but Benfica have two away goals under their belts, as well as a record of 15 wins, three draws and one defeat in their last 19 European home games. Lyon will also take a narrow lead into Wednesday\'s game at Cypriot side APOEL FC, whose hopes of reaching the last eight remain alive despite a 1-0 loss at Stade Gerland in the first leg. OL are bidding to reach the quarter-finals for the first time since their run to the last four in 2009-10 but domestically they are without a win in five Ligue 1 matches, which has seen them fall seven points below the Champions League places. \"The match in Nicosia on Wednesday is important for the players, but also for the club,\" said Lyon coach Remi Garde after Saturday\'s 2-0 loss at Nancy.