Arsenal manager Mikel Arteta has sought to explain his decision not to play both Nicolas Pepe and Gabriel Martinelli in the Gunners' 3-2 win over Benfica on Thursday night.
The Gunners advanced to the last 16 of the Europa League after a hard-fought win against the Portuguese side, with captain Pierre-Emerick Aubameyang grabbing a brace on either side of a Kieran Tierney goal.
There was no place for Pepe, who has been sensational in the competition for Arteta's team, and the Spaniard gave the reason why after the match.
"Because there wasn't much space to run in behind," he responded to the question of why Pepe and Martinelli did not play.
"It was a really tight two lines, 4-4-1-1, or 5-3-2 at times, they were a really, really low block, not much space to run apart from when they set the line around the 18-yard box. You need people to unlock that, with special qualities in tight spaces to create movement and I think Willi was really helpful tonight," he added.
The Gunners qualified on a 4-3 aggregate win, following their 1-1 draw in the first leg, and will be in the draw set for Friday afternoon.
They could be drawn against any of the teams, including the two remaining English clubs, Man United and Tottenham, a fact Arteta understands.
"You never know! In this draw there’s going to be some funny games because there are a lot of teams left in the competition still. Let’s see,"
Next up for the Gunners is a Premier League clash against Leicester, on Sunday.