Alexandre Lacazette was forced off with an injury during Arsenal's 1-1 draw with Fulham on Sunday.
The striker went down in 70th minute of the Premier League encounter and had to be substituted when Fulham were 1-0 up through a penalty from Josh Maja.
Eddie Nketiah replaced the France international when he headed down the tunnel for treatment, and went on to fire in the equaliser just seconds before the final whistle.
What happened to Lacazette?
The 29-year-old pulled up holding the back of his leg after an Arsenal attack. The injury appeared to be a hamstring problem.
Lacazette is the Gunners' top scorer this season having scored 17 goals in 38 appearances in all competitions, netting 13 in the Premier League.
Nketiah was happy to step up and make the difference for his side after coming off the bench, but wished his team-mate well in his recovery from the injury.
"Firstly I wish Laca a speedy recovery - he's important to the team and hopefully will be back as soon as possible," he told Sky Sports.
"For me I stay patient and I'm happy to get the chance to play and I will be ready to help the team if I'm called upon."
Arteta provides Lacazette update
Arsenal boss Mikel Arteta confirmed that the attacker sustained a hamstring injury and believes the fact he has now played three games in the space of seven days may have played a role.
He said to Sky Sports: "He felt his hamstring so we don't know. We have to rotate players, we have players who didn't recover from the game on Thursday. That is the risk.
"You cannot change those players every game."
Arsenal's injury list grows
The loss of the former Lyon star adds to Arteta's injury concerns as his side compete in the Europa League semi-finals and climb up the Premier League table.
Arsenal are already without Pierre-Emerick Aubameyang after the striker contracted malaria. Meanwhile, defenders Kieran Tierney and David Luiz and midfielder Martin Odegaard are also out injured.
What next for Arsenal?
After the draw with Fulham, Arsenal turn their attention to next Friday's Premier League match against Everton. They will then face Villarreal in the first leg of their Europa League semi-final tie six days later, followed by a trip to Newcastle on May 1.