Koscielny played 72 minutes in Arsenal's final Europa League group game having not featured since rupturing his Achilles in the semi-final of the same competition against Atletico Madrid last May.
"Today Saka also played with a good performance, with a very big personality and we were speaking at half-time". I think for Koscielny it's good that he's recovered and I also think he recovered in a good time from his big injury. They show us in every match positive things. I prefer to use, if we can, a specialist centre-back'.
Rob Holding and Konstantinos Mavropanos are injured, while Sokratis Papastathopoulos and Shkodran Mustafi are banned - meaning Koscielny is Emery's only fit recognised centre-back, but the Spaniard is keen not to ask too much of his skipper.
"Not every action was good for us, but his personality is very important to continue in the second half trying to do one-on-ones and break lines with his quality".
Koscielny's return to fitness could prove timely for Emery, who has something of a defensive crisis heading into Sunday's Premier League trip to Southampton.
Here are the winners and losers from the new farm bill
One way to gauge the bill's winners and losers is the ways various organizations responded to the relatively speedy approval. As farmers enter loan renewal season, having a five-year bill is key for producers weathering tough economic times.
"First we needed to have the mix of the first XI with young players", he said.
'Two weeks ago we played in Kiev and it was the same with Emile and Willock, who scored there.
"I don't know. Tomorrow he is in the group, there are 18 players in the squad for this match and I am going to decide if he plays tomorrow from the beginning or during the match in the 90 minutes".
"It was very important to keep our unbeaten run going for the confidence and now we start a big challenge ahead of Christmas".
"We are going to decide but the first is to think about the match tomorrow because we need to receive information on how he can feel".