The Germany international made two good second-half saves to keep his side in the game, but his positioning was poor for Insigne's goal.
Made two important interceptions and kept Higuain quiet, while also monitoring the movement of Callejon, who was always looking to come inside Durm and threaten more centrally.
A solid performance, as the inexperienced full-back didn't allow Callejon to get the better of him too often, though he didn't offer much in attack.
The Armenia international was in majestic form, gliding around opponents and taking the game to Napoli. Unfortunate to see several good efforts thwarted by Reina.
Made a key mistake in the build-up to Insigne's second-half goal, and was worryingly wasteful with the ball on several occasions.
Took his goal brilliantly, slotting the ball composedly through the legs of Reina. Offered plenty of energy both going forward and in attack and made intelligent runs.
Worked hard to ensure that Mertens had little effect in the first half, but struggled to deal with Insigne cutting inside. Showed his versatility through playing at both full-back and on the wing.
Played a few testing balls into the area and was much more economical with his use of the ball in comparison to his midfield partner.
Took his penalty exceptionally coolly in a high-pressure situation, and his pace offered Dortmund a constant outlet down the left. Made the key run and pass for Blaszczykowski's goal.
Performed admirably out of position, making several great headers and interceptions to prevent Higuain from peeling off at the back post or linking up with Pandev.
Didn't get the goal that he would have liked, as Reina was in top form to deny the Polish striker on several occasions. His ability to bring others into play didn't go unnoticed.
Made a range of excellent saves to keep Napoli in the game until the dying minutes.
His pace was useful on the overlap in the first half, but the Colombian was somewhat nullified by the poor game that Mertens endured.
Made a couple of important clearances, but struggled to deal with the physical presence of Lewandowski throughout.
Should have been penalised for impeding Lewandowski inside the penalty area and the Argentine was generally off the pace.
His battling qualities can always be valued in a tough away fixture and the Swiss midfielder showed his customary grit.
Showed glimpses of skill and a nice touch but struggled to create a great deal in a rather lacklustre Napoli midfield.
Made an excellent last-ditch challenge to deny Lewandowski the opportunity to poke home at the back post and worked hard.
Had one golden opportunity that was saved by Weidenfeller, but the former Real Madrid man didn't get a great deal of quality service.
A rather poor game from the Belgian, who really struggled to get into the game in the first half. Was less wasteful in the second, aside from his poor free kicks.
Struck the foot of the post in the first half, but was otherwise ineffectual, failing to get the better of Durm too often.
Struggled to link up with Higuain and didn't carve out any chances for himself. Wasn't provided with the best service, but didn't stand out whatsoever.