Arsenal will face Villarreal or Valencia in the last four if they can get past Napoli, with the first leg switched to the Emirates to avoid two ties being played in London on the same night.
Arsenal needed a fast start and they got one, opening the scoring in the fifth minute when Maitland-Niles and Aaron Ramsey combined down the right channel to tee up Aubameyang for a simple close-range finish.
In the past Arsenal have struggled to break down sides, and they still do sometimes, but the striker's performance today won the match.
'I was really happy (when I heard I could play),' he said, having missed the defeat in Rennes. Upon further inspection, Aubameyang was offside in the lead-up to the goal, and Rennes will feel hard-done by the lack of VAR and the incompetence of the officiating.
However, it was not forthcoming and with VAR not in operation in the Europa League unlike the more lucrative Champions League, Maitland-Niles's downward header from Aubameyang's cross was allowed to stand.
He has reason to complain, though.
Since then though he has positioned the team in fourth spot in the Premier League with eight games of the season to go.
Kalidou Koulibaly salutes the Napoli fans
"We can be proud of our supporters and players today because it has been a very hard week", he said, per Sky Sports.
Following their 2-0 win over Manchester United on Sunday, success in the Europa League appeared a little less urgent, and victory here marks a return to form under Emery.
"I think they [Rennes] were a bit nervous and angry as well", Aubameyang added.
"Today, Inter (Milan) are out, Sevilla are out - a big surprise".
"If you can see the quality of the football every weekend and midweek [in the Premier League], it is getting more and more competitive", said Cech, who is set to retire at the end of the season. "So, for me, it will be very hard to play against them in Naples".
"Playing under pressure is good".