Mikel Arteta has praised the reaction of Pierre-Emerick Aubameyang after his skipper missed a last-gasp chance as Arsenal crashed out of the Europa League to Olympiacos.

The Gunners lost 2-1 after extra time at the Emirates Stadium on Thursday night, meaning they were knocked out on away goals.

Aubameyang had equalised with just six minutes remaining, only for Youssef El Arabi to sweep home late on and send the Greek side through to the round of 16.

But it could have been different had Aubameyang, Arsenal's top goalscorer this season, converted another chance just moments after the decisive goal.

The 30-year-old apologised after the game but Arteta was pleased with how the Gabon international responded to the setback.

"He was gutted," Arteta said of Aubameyang.

"Obviously he scored a wonder goal that was putting us through in the competition, and with the last kick of the game, he had the best chance of the game.

"He felt very responsible about it, we will try to be right behind him. He has been phenomenal all season for us and now the players have to support him.

"I think his reaction after the game – to face the media and the way he talked, it was a very mature reaction from him."

Arteta had his players back on the training ground on Saturday for the first time since Thursday's Europa League elimination.

He admitted the players were left "very down, frustrated, disappointed" by the defeat but is keen to extend their FA Cup run by beating Portsmouth at Fratton Park on Monday night.

"It's really special," he said of a competition he won twice as a player at Arsenal.

"It's probably one of the nicest games and days of the season when you play the final day in England, at Wembley, nice weather and an incredible atmosphere.

"And you know, it's a trophy that's been very much linked with our history. So we want to continue to be attached to that, knowing that on Monday night in Portsmouth, it will be tough."

While Arteta could rotate his side on the south coast, Sead Kolasinac will still be missing after it emerged he suffered a significant shoulder strain in the win over Everton last weekend.

The blow will be softened by the fact fellow left-back Kieran Tierney is back in full training following his own shoulder problem, with Arteta not ruling the Scotland international out of Monday's game.

"He is much closer," he added.

"He is evolving really well. He feels fit. He feels confident now. He's doing the stuff with contact, so hopefully we can have him soon."