Arsenal vs Borussia Dortmund: Three things we learned as Ethan Nwaneri impresses again

Arsenal's 3-2 defeat to Borussia Dortmund exposed several issues Mikel Arteta will need to solve before the new season, but there were also encouraging signs from some of the club's younger and newer faces.

With several key players still unavailable, the Gunners looked vulnerable defensively, while Ethan Nwaneri and Christos Tzolis both strengthened their cases for bigger roles.

Dortmund repeatedly found space through the middle of the pitch and punished Arsenal's defensive structure.

Without William Saliba, Declan Rice and new signing Bruno Guimaraes, the Gunners lacked the physical presence that normally protects their back line. Riccardo Calafiori's adventurous positioning also left Arsenal exposed on several occasions, with Dortmund taking full advantage.

While Arteta will expect significant improvement once his strongest XI is available, the performance highlighted how important his defensive leaders remain.

Christos Tzolis was one of Arsenal's brightest performers despite the defeat.

The winger caused problems from set-pieces throughout the first half before becoming increasingly influential after the interval. He supplied the assist for Ethan Nwaneri's goal with an excellent cross and later won a penalty after another direct run.

After arriving with relatively little attention this summer, Tzolis has made an encouraging early impression with his pace, creativity and willingness to attack defenders.

Ethan Nwaneri also made the most of his opportunity after replacing Martin Odegaard during the first half.

The teenager showed intelligence in possession, worked hard without the ball and capped his display with a well-taken goal after Tzolis' cross.

His energetic performance comes at an important time, with uncertainty continuing to surround his long-term future at Arsenal following last season's loan spell.

If he can continue producing displays like this, Arteta may think twice before allowing the academy graduate to leave.

Arsenal now turn their attention to the Community Shield before opening their Premier League title defence against Coventry City. Arteta will hope the return of several World Cup players and Bruno Guimaraes provides the balance his side lacked against Borussia Dortmund.