Unai Emery is fearing the worst after Rob Holding suffered a "big injury" to his knee against Manchester United on Wednesday.
The Arsenal boss was proud of his side's performance in their 2-2 draw at Manchester United, which was marred by injuries to Holding and Aaron Ramsey.
Arsenal twice took the lead at Old Trafford through Shkodran Mustafi and Marcos Rojo's own goal, but equalisers from Anthony Martial and Jesse Lingard ensured a share of the spoils in the Premier League on Wednesday.
Emery's men are now unbeaten in 20 games in all competitions, but the result was tainted by first-half injuries to Holding and Ramsey, who both had to be substituted.
Emery thinks Ramsey's is just "a small injury" but fears Holding could be out for some time, and the Gunners head coach praised his side for responding well to those setbacks.
"[It was] the worst news for us," he told a news conference. "Rob Holding, we are going to wait for the doctors, but it is a big injury. It's his knee.
"After these two injuries, every player went out with good commitment and good mentality to keep our performance on the game.
"We couldn't control for the full 90 minutes. This draw is not the best, but not the worst. I said to the players now we need to finish this week well [against Huddersfield Town].
"I am very proud for our work and how every player responded in the 90 minutes. When we are winning, it was a good moment, but they equalised very quickly.
"The second half, I think our players worked to win. We were close more than them to get the third goal, but [David] De Gea made good saves."
The news of potentially losing Holding is a blow but Emery is confident Laurent Koscielny is close to fitness, having played for the Under-23 side this week.
"Laurent is very close to playing," he said. "He played two matches for the Under-23s, the last on Tuesday. We are thinking he will start with us soon.
"I don't know if Saturday is a possibility. We are thinking the Europa League against Qarabag is a possibility [next Thursday]."
Emery feels Arsenal are becoming more of a match for the top sides in the Premier League, having limited United to few clear-cut chances.
"Our challenge is to come to teams like United, I think today our response was positive," he said. "We are getting better competitively. Usually, United create a lot of chances here. They didn't tonight."
There was a suggestion Ander Herrera was offside in the build-up to United's first goal, while there were some appeals for Rojo to be sent off for a challenge on Matteo Guendouzi, but Emery refused to blame the officials for costing his side a win.
"I know VAR is coming. When it's coming, it can equalise something like these difficult decisions," he added. "I know maybe he was offside, but it was very difficult. I think the referee's decision is not important today for the result."