Carlisle United are facing an anxious wait over the latest injury suffered by luckless striker Ryan Edmondson.
The frontman, in his first start for a month after a hip problem, had to go off in the first half of the draw with Rochdale because of an ankle injury.
The former Leeds United man left Brunton Park wearing a protective boot after the 3-3 draw.
Simpson said the full extent of the injury would not be clear for a few days.
“I asked Ross [Goodwin, Carlisle’s physio] at half-time about it and he said it’s swollen up already,” Simpson said.
CARLISLE UNITED 3-3 ROCHDALE - AS IT HAPPENED
“It may just be a grade one, which reacts straight away – he’s iced it straight away, he’s got in the boot to take him off his feet.
“We’ll assess it probably on Monday. The first 48 hours are important just to let it settle down. We’ll see how he goes.
“It’s really frustrating for him – he’s just got himself back, and worked extremely hard to get back, but we’ll asses it over the next few days.”
Edmondson suffered the injury early in the clash with Rochdale and failed to run it off, eventually being replaced by Omari Patrick midway through the first half.
“I’ve got to say it was a stupid challenge from him in the far corner,” said Simpson of Edmondson.
“He’s got the centre-back going nowhere, and it’s not a massive push but enough for their player to go down and the referee to give them a free kick, and as their centre-back landed on Edmo he’s just done a bit of a scissor tackle on his ankle and he’s twisted it.
"He kept telling me he was ok but we could see he wasn’t running ok. I maybe have to hold my hands up and say I should have got him off earlier, so that he wasn’t put into that situation, but he kept saying he was fine.
"Sometimes when you have an ankle twist it’s really painful, but you can get through it after a few minutes.
"He was frustrated when he walked off, but we'll let the dust settle, and I’ll speak to him tomorrow or Monday to see how he is."
Simpson was less concerned over goalscorer Paul Huntington, who also had to be replaced before the end of the game.
The experienced defender’s 88th-minute withdrawal was because of cramp, the manager said.
The latest injury absentee, meanwhile, was Callum Guy with a groin problem.
But Simpson said the midfielder could be back in contention for United’s next game at Harrogate Town next Saturday.
“I felt it right to give Callum a break on Tuesday [by leaving him out of the Papa John’s Trophy game against Manchester United Under-21s] but he trained,” Simpson said.
“The last thing he did [in the session] was go for a side-foot finish, and he’s felt something in his groin.
“I’m told it’s a grade one strain which is a seven-to-ten day job, so hopefully he’ll be back next weekend.”
United have endured an injury-hit run since the start of the campaign and Simpson added: “It’s happening right through the team unfortunately. I suppose it is the nature of our game at the moment.
“We are obsessed with injury prevention and caution and making sure players are right and all this sort of stuff.
“It's annoying but it’s part of the game, part of what we have to accept, and understand that it’s going to happen.
“I’d really like to have a run where we can have a clear path at it and I can make selection decisions because everybody’s available.”
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