Mikel Arteta has warned Emiliano Martinez he must prove he is a superior option to Bernd Leno if he is to get game time in goal for Arsenal.
The Gunners operated with a policy of using separate goalkeepers for Premier League competitions under both Arsene Wenger and Unai Emery with Martinez starting each of the six Europa League group stages games this season.
However Arteta opted to break with tradition for the round of 32 tie against Olympiacos in which No.1 Leno started each game, though it was not an entirely successful gambit as the German's late error handed the Greek champions victory at the Emirates Stadium on Thursday night.
Still Arteta was not prepared to offer Martinez any guarantees over his starting spot for Monday night's FA Cup fifth round tie against Portsmouth even if the Argentine has started in both of the previous rounds.
"I like to play the player that I think is in the best condition for that game," Arteta said. "If it is Emi, it is Emi, And if it's Bernd, it's Bernd.
"It is the same with the right-backs or the centre-backs.
"Because they played on Thursday night, I am not going to say 'oh, they cannot play on Monday'. If I send that message to them, they are going to be tired, they are mentally not going to be prepared. In my opinion, it is not right."
He added: "I don't make any difference between goalkeepers, full-back, strikers, attacking midfielders.
"They are all the same. They are part of the squad.
"We try to make the decision based on who we believe is better to win that competition. Players have to respect that, fight and compete between them.
"And if I made a wrong decision, probably sometimes I will do."
Arteta's comments may prompt further doubt over Martinez's long-term future at Arsenal.
The 27-year-old enjoyed a successful spell at Reading in the second half of last season but opted to remain at the Emirates Stadium following assurances he would be given the game time to compete with Leno.
Martinez will have two years remaining on his contract with Arsenal at the end of the season.
