From tactical one-upmanship to Unai Emery's expert use of the bench, UEFA.com's reporters take us through the big talking points from the quarter-final first legs.
Article top media content
Strength in depth saves Sevilla's day
Off the pace and trailing to a 29th-minute goal from FC Zenit's Aleksandr Ryazantsev, defending champions Sevilla FC trudged off the pitch at half-time with boos from their fans ringing in their ears at the Estadio Ramón Sánchez Pizjuán.
Yet Los Hispalenses have a deep and shrewdly assembled squad, and coach Unai Emery was able to bring on Stéphane Mbia – so often his club's talisman in this competition – and 21-year-old on-loan FC Barcelona schemer Denis Suárez at the interval. Their introductions, along with a greater level of impetus all round, helped crank up the pressure on the resilient visitors as the Spanish side started on the front foot after the restart.
Still the Russian team held out, until a third change – Carlos Bacca replacing Kevin Gameiro – tipped the balance. The Colombian forward headed home in the 73rd-minute, followed 15 minutes later by an exquisitely volleyed winner from Suárez. Denied the services of Sine-belo-golubye regulars Hulk, Danny, Igor Smolnikov and Domenico Criscito through suspension, such game-changing substitutes were out of André Villas-Boas' reach. Nick Aitken
Wolfsburg eye unprecedented comeback
"It sounds odd, but it is not over. We'll do all we can to achieve a feat nobody thinks we're capable of," declared VfL Wolfsburg goalkeeper Diego Benaglio, after the Bundesliga side suffered their heaviest-ever home defeat in Europe.
No side has ever overturned a three-goal deficit from a home game in a UEFA club competition tie, meaning the Wolves will have to break new ground in Naples – where the Serie A side are unbeaten in 11 outings in Europe. Additionally, of the sides that started out in the group stage, Napoli have conceded the fewest goals in their 11 games: just five. "If we manage to go through to the semi-finals after this result … It will be sensational," admitted Wolfsburg coach Dieter Hecking.
Meanwhile, experienced tactician Rafael Benítez refused to get carried away in the aftermath of the Partenopei's first UEFA competition win in Germany: "We have a lot of respect for Wolfsburg – they're a very good team and in football you never know. You have to concentrate and if we play a good game then we have a great advantage – but we still have to play 90 minutes." Matthias Rötters
Montella's tactics outfox Dynamo
"We don't often play against teams with three-man defences but I hope our players will use the information we gave them," said FC Dynamo Kyiv coach Serhiy Rebrov before the Bilo-Syni's 1-1 draw against ACF Fiorentina. Vincenzo Montella had fielded a 3-5-2 formation in the Viola's last three away outings in the competition, but in Kyiv he sprung a surprise by opting for a more attacking 4-3-3.
"We studied them well and we knew what we'd see today," said Dynamo goalscorer Jeremain Lens, however from the stands it looked as though the hosts weren't prepared for Fiorentina's tactical switch.
The intense pressing game pushed Dynamo back into their own half, forcing the likes of Andriy Yarmolenko, Lens and Serhiy Sydorchuk to defend deep. On the occasions the Ukrainian side regained possession, they had almost no energy left to threaten Neto's goal.
Despite being overwhelmed for much of the first period, Rebrov's team broke the deadlock – against the run of play. An unlikely victory was within reach, but perhaps the hosts sat too deep in the closing stages and invited pressure as substitute Khouma Babacar's added-time equaliser earned the Serie A side a deserved draw.
The late blow came as a shock to the Ukrainian side at the time, but in the context of the 90 minutes it was a fair return for the visitors' efforts – an assessment expressed by the Dynamo players after the game. Bogdan Buga
Markevych's mind games
"We cannot win the Europa League," Myron Markevych said on the eve of his team's 0-0 draw at Club Brugge KV, the FC Dnipro Dnipropetrovsk coach making a statement so striking for a team already through to the last eight that many media outlets reported he had said the exact opposite.
The wily 64-year-old may have been thinking about the high-calibre clubs still in the running, but more plausibly he was just taking the pressure off his players. After all, his side were well worth their result and came close to ending Club Brugge's unbeaten record in the UEFA Europa League this season. As Blauw-Zwart boss Michel Preud'homme underlined: "Dnipro are perhaps the most complete team we have faced in the competition."
Win in Kyiv next week and the Ukrainian hopefuls will be just two matches from the final, surely close enough that anything can happen – including a Dnipro triumph. Indeed, judging by the comments of captain Ruslan Rotan, his players are certainly setting themselves no limits: "Step by step, we want to try to win every game." Chris Burke