Benfica arrive at San Siro with five straight wins and 15 goals behind them. AC Milan are unbeaten in Serie A. For two clubs used to Europe's biggest nights, the Europa League begins with a proper test.
A heavyweight opening night
This is only the first match of the league phase, but neither side will want to spend the autumn chasing points after a slow start. Milan have home advantage and an unbeaten league record; Benfica arrive with the sharper winning streak.
The setting adds to the sense of occasion. San Siro under the lights is familiar European territory, yet the new campaign gives both teams a blank page. An early win would bring belief as well as three valuable points.
Milan have been hard to shift
Milan have taken two wins and two draws from their opening four Serie A matches. They beat Torino 2-1 and Venezia 2-0 before drawing away to Juventus and Lazio, scoring seven goals and conceding four across that run.
The two away draws matter. Milan had to respond in different surroundings and stayed unbeaten, but Benfica will ask a fresh question: can the Rossoneri control a European home game against opponents carrying real momentum?
Benfica arrive in full stride
Benfica have won their latest five competitive matches, scoring 15 goals and conceding only three. Their league run includes a 3-0 win at Marítimo, four without reply at Moreirense and Sunday's 3-1 victory over Gil Vicente.
They also came through their Europa League play-off trip to AGF with a 3-1 win. That result settles nothing in Milan, but it means Benfica arrive knowing their attacking game has worked away from Lisbon.
Where the match may turn
The opening half-hour should tell us plenty. Milan will want the crowd involved and the match played on their terms. Benfica have enough recent scoring form to punish any loose spell, so the hosts cannot afford to let the evening become stretched too early.
For Benfica, the challenge is to keep their confidence without giving Milan space to attack. If they can withstand the first surge and carry a threat of their own, San Siro could be set for a tense second half.
Match details
AC Milan v Benfica
Wednesday 16 September, 20:00 BST
UEFA Europa League, league phase
San Siro
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What to watch
Milan's unbeaten start has been built on staying composed when matches become difficult. Benfica's five-game winning run has carried more attacking punch. The side that imposes its rhythm first will have the best chance of turning a glamorous opening night into a valuable one.