Trippier told the bench he needed to come off and pointed to his calf but it remains to be seen how much damage he has suffered.
Howe said: "I think Kieran's got a slight calf issue.
"He motioned that he needed to come off, so we'll have to see how that is.
"It would be devastating to lose him in the form he's in."
United now face Aston Villa on Sunday.
Howe added: "We're seeing the togetherness.
"We're in a relegation battle, and we need to stick together and fight for everything.
"It's not going to be perfect football, it's not going to be perfect games at this moment, but we're in a position where we have to find a way to win, even if we're not playing at our best.
"We have to stay in games and be competitive, and I thought we were tonight.
"We did a lot of the off-the-ball stuff really well, and I was really, really pleased with the commitment."
Need a VPN? Or seeking to switch? Then support Tribal Football by clicking here to sign up with our official partners NordVPN. Not only will you receive the best VPN experience, but also great discounts by signing up via Tribal Football. Thanks for your support!