Arsenal played out a 0-0 Europa League draw with Sporting on Thursday to confirm their progression to the knockout stages.
But the game was overshadowed by Welbeck’s first-half injury, with the England international stretchered off after falling awkwardly on his ankle.
There has been no official confirmation of the injury, nor a timescale placed on his return just yet, but Emery did say it was “serious”.
“The worst news tonight are these injuries,” Emery said. “We think it’s a serious injury.
“Every injury is different. He broke something in his ankle and it’s a different injury than another.
“Now he’s at the hospital and the news is at the moment we are going to wait, but we think this is a serious injury.”