Alexandre Lacazette is back in full training again and nearing a first-team return - but why does the boss often take him off in the second half of games?
Arsene Wenger sat down with us to discuss the use of stats to determine players' physical conditions - and revealed how he manages the France international.
"We know the players’ physical qualities and who we expect to drop in the second half or not," the boss told the Arsenal Magazine. "Nobody’s tired enough at half time to be substituted for that, but in the second half you’ll see that sometimes this player will drop in the last 20 minutes.
"We have a fatigue factor coming in at different levels for everybody and we know the players who drop more in the second half than others. Some remain completely consistent and some even push upwards in the second half.
"There are players who drop up to 15 per cent in the second half, so you have to consider that in your substitutions. Even if you do make substitutions, you always try to keep one free because you know this guy could need to be substituted as well so you need to keep a place for him.
"I must say that [Lacazette] plays in a position where you sub more than say a defender," Wenger added. "You substitute a striker more than you would a defender, because they always have to provoke, to defend, to attack, you have to create holes in the defences. The strikers are more subbed than others.
"Secondly, he was in an adaptation period where I felt that, without any objective measurement, that sometimes he struggled a bit more in the second part of the game, especially in the last 20 minutes, to create the movement he can.
"I put that down to an adaptation period. It was not so much physically - that didn’t drop so much - it just looked like he was a bit less sharp."
Copyright 2018 The Arsenal Football Club plc. Permission to use quotations from this article is granted subject to appropriate credit being given to www.arsenal.com as the source.