Arsenal manager Mikel Arteta admits he brought on Martin Odegaard and Thomas Partey against Olympiacos to give his side 'more control'.
The Gunners went down 1-0 against the Greek side but managed to prevail with a 3-2 victory on aggregate.
"We needed more control," explained Arteta when asked about the substitutions.
"We needed to put some passes together. You can't always play football trying to attack in two or three touches, that led to a lot of balls lost and when the forwards are running and the backline are squeezing, there's a lot of transition moments.
"I wasn't happy at all with that and we needed more stability and, after the substitutions, we were better."