Arsenal coach Mikel Arteta said he was "worried" about Gabriel Jesus after the Brazilian forward was taken off with a hamstring injury in the 2-1 Champions League win over Sevilla on Tuesday.
The Brazil international scored a stunning goal and created another for compatriot Gabriel Martinelli as the Gunners got their European campaign back on track after a defeat at Lens.
Arteta lavished praise on the forward but admitted his concern over the injury which forced him off late in the game.
"He hurt something in his hamstring and he had to come off, I'm worried about that," Arteta told reporters in Seville.
Jesus started the season with a knee injury and only made his first start late in September, looking for his best form.
Although the striker has only scored one Premier League goal in seven appearances, he has three in three in the Champions League.
Jesus's slick turn helped crack open Sevilla's defence and he threaded a pass through for Martinelli to open the scoring just before halftime.
Then Jesus added the second himself with a fine strike into the top corner, and it proved decisive after Nemanja Gudelj headed home from a corner.
"I'm really happy, (it was a) big game for big players, he needs to produce those moments," said Arteta.
"He came here for a reason, he changed our world, he brought so much belief and energy for the team. The team relies on those players to win games, we need players like this."
Arsenal are third in the Premier League, two points behind leaders Tottenham, and may have to turn to Eddie Nketiah, Kai Havertz or Leandro Trossard to fill the gap left by Jesus, if his injury proves serious.
The Gunners host Sheffield United on Saturday before visiting Newcastle in the top flight, and then host Sevilla in the Champions League.
Arteta said the team's victory at Sevilla's Ramon Sanchez Pizjuan stadium, which took the Gunners top of Group B after Lens drew 1-1 against PSV Eindhoven, was important.
"We took a big step towards qualification, it's another step, this team has to keep growing," added the coach.
"Defeat against Lens put us in a difficult position and we had to react."