The former Rangers and Aberdeen star was part of the BBC’s punditry team for the match at Station Park.
In the warm-up, Dundee United No.1 Benjamin Siegrist had to be replaced by Deniz Mehmet after sustaining an injury to his hand.
Foster said: “This might sound horrible but I hope he’s broken his wrist or his hand because otherwise just wrap it up and get out there and play.
“It didn’t look like he was in too much distress, it looked like he had a wee sore wrist and he’s came off.
“If it’s not a serious injury then just strap it up and play on.”
The comments were labelled “pathetic” by one United fan.
Manager Micky Melon confirmed after the match that Siegrist will go for a scan and was in “quite a lot of pain”.