Ricardo Rodriguez marked his competitive AC Milan debut with what proved to be the winning goal in a 1-0 away victory over CSU Craiova in the UEFA Europa League third qualifying round first leg.

Milan has enjoyed an extremely busy transfer window as it pushes for a return to the UEFA Champions League and former Wolfsburg defender Rodriguez was one of four new signings to start in Romania.

Fabio Borini, Mateo Musacchio and Franck Kessie joined him in the starting XI, with Andre Silva and Andrea Conti on the bench and headline addition Leonardo Bonucci, Lucas Biglia and Hakan Calhanoglu not in the squad.

After a slow start by the Serie A side, it was Rodriguez who made the decisive impact shortly before half-time.

The full-back has long since been a danger from set-pieces and found the net with a free-kick to give Milan an away goal.

Chances to take complete command of the tie in the second half were spurned, while Craiova — making its European debut — also had opportunities, but Milan should be very confident of completing the job at San Siro next week after Friday's (AEST) largely dominant showing.

It took Milan until the 20th minute to register a shot on target, M'Baye Niang's effort held easily by Nicolae Calancea.

Three minutes later it would have been behind had Gianluigi Donnarumma, who ended a long saga by signing a new contract this month, not produced another demonstration of his worth to keep out Ionut Mitrita's scuffed effort after the midfielder had broken through on goal.

Milan then went agonisingly close to taking the lead itself when Patrick Cutrone struck the inside of the post from a tight angle and saw the ball roll across the face of the goal.

The impressive Cutrone looped a header over the crossbar from a corner as Milan began to take control of the contest.

Rodriguez was bullied off the ball and stopped from rounding Calancea by Hrvoje Spahija, but the Switzerland international did break the deadlock in the 44th minute.

Borini won a free-kick on the right flank and Rodriguez's whipped delivery found the bottom-left corner despite no Milan player getting a touch on it in the box.

Milan kept its foot on the accelerator after the break and Niang saw a pair of opportunities go begging. First the Frenchman curled over before being denied at the near post by Calancea.

Giacomo Bonaventura and Borini both failed to hit the target with speculative efforts and Craiova continued to offer a threat at the other end, Mitrita bending wide with Donnarumma stranded after a poor clearing punch from a free-kick.

Cutrone could not capitalise on Calancea's inability to collect a corner as he failed to get the direction on his header.

Silva was then brought on to replace Borini and make his competitive debut, but Craiova grew in confidence going forward, with Donnarumma looking increasingly shaky in the Milan goal.

The second goal always looked more likely to come from the visitors, though, and Vincenzo Montella can be satisfied with his team's efforts as Milan marked its return to European competition after a three-season absence with a deserved win.