Not for the first time since arriving at Arsenal, Unai Emery changed a game from the touchline with a string of imaginative substitutions on Monday night.

Under Arsene Wenger frustration would grow at the Emirates as he persisted with plan A and tended to make changes in personnel rather than tactics. Emery has instead taken a proactive approach to his job. He notices problems in-game and acts on them.

This has not always been by design. Part of the reason he has been forced to make changes is because Arsenal have started matches too slowly. They have conceded first in four of their nine games, and been drawing at half time on eight occasions.

That was the case again on Monday night when, having gone behind through Hector Bellerin's own goal, Arsenal clawed their way back into the game just before half time. They were level at the break again, and the momentum had shifted, but 15 minutes into the second half Emery still wasn't happy, he wanted more.

Pierre-Emerick Aubameyang and Matteo Guendouzi came on, replacing the anonymous Henrikh Mkhitaryan and an out-of-position Stephan Lichsteiner at left-back.

A murmur of excitement mixed with confusion fizzed around the ground. Is this three-at-the-back, with Bellerin as a centre-back? Is Guendouzi going to left-back? Is Aubameyang going to play as an attacking kind of left wing-back?!