Ross Stewart is Sunderland's top scorer despite missing a large part of the season
Sunderland striker Ross Stewart faces an anxious wait to discover the extent of his Achilles injury.
The Scotland international was stretchered off 20 minutes into Saturday's 1-1 draw with Fulham in the FA Cup fourth round.
Manager Tony Mowbray fears "it's a bad injury" but will await scan results.
It is the second notable injury Stewart has sustained this season after a thigh injury in September kept him out for nearly four months and 15 league games.
The former Ross County forward has scored in five of the six Championship games since his return, and has 11 goals and three assists in 15 games in total this season.
Mowbray told BBC Radio Newcastle: "First thoughts is it's pretty bad. If it's an Achilles - we've discussed whether it's ruptured, but it's a bad injury.
"Hopefully it's just strained and it's not so bad, but let's wait and see. It's no good me telling you it's really bad or it's not so bad, let's wait and see what the scan shows, but we know he's got a protective boot on his foot."
Mowbray hinted the Black Cats' mounting injury crisis - which saw 15-year-old Chris Rigg feature in the latter stages at Craven Cottage - could force him into action before the transfer window closes.
He added: "We've got a big few days coming up because if the injuries are bad - we lost Corry Evans in the week - we need some reinforcements or we'll have to play 18 league games with a team of kids.
"That feels a bit dramatic because the kids have shown they can compete with a Premier League side, so we shouldn't fear that."
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