Mikel Arteta was unsure when Pierre-Emerick Aubameyang would return as he reflected on a "really sad" FA Cup elimination for Arsenal.
The Gunners went down to a 1-0 defeat at Southampton on Saturday, their hopes of retaining the trophy ended in the fourth round.
Arsenal played without captain Aubameyang, who had to leave the team in the hours before kick-off for personal reasons.
Amid reports attacking midfielder Martin Odegaard is set to join from Real Madrid, Arteta expressed regret at his side's exit.
"Really sad to be out of the competition," he said to BT Sport. "Disappointed to be out and the way we conceded.
"We are looking in the market and will see what we can do."
The teams meet again at St Mary's on Tuesday for a Premier League clash and Arteta is unsure whether Aubameyang will be back.
"I don't know, he needs to address that issue and see how it evolves," the Arsenal boss said at his post-match news conference.
"We are here, we will have to support him. He needs to take the time that is needed because that is a priority at the moment."
Gabriel Magalhaes' first-half own goal settled a scrappy contest where Arteta felt Arsenal had improved after the break.
Arteta added: "We had issues in the first half and unforced errors as a result of the high-press they do.
"In the second half we had two or three big chances but not enough. It was an even game.
"In the first half they won a lot of second balls. In the second half we added more quality. We became more dominant and created chances but it wasn't enough."
Arsenal have conceded four own goals in all competitions this season.
Opta statistics show this is more than any other Premier League side and the most they have conceded in a single season since 2015-16 (five).
Asked if Gabriel had been rusty, Arteta said: "Maybe. He hasn't played enough minutes in the last month or so since he had the Covid.
"He had to stay at home, he hasn't trained as much as we would like him to. He is a player that has done so well since he has joined us. Credit to Southampton because they make it really hard for you."
Southampton boss Ralph Hasenhuttl was impressed with the way his team played, though suggested it had not been a perfect display.
"It was a good team performance," he said. "In general our work without the ball was good.
"We had in the first half more punch and more power. In the second half it's normal they have a lift. We must make the second goal.
"We made one or two chances - Shane Long should have got a penalty. We had early ball wins, but our last decision-making was not always the best."
Arsenal have now failed to make the fifth round of the FA Cup in three of the last four seasons.