Cajuste turned his ankle in the 4-1 defeat to Spurs, while Phillips picked up a calf issue.
Both midfielders will be assessed ahead of the game at Old Trafford, which has developed into a shock possible relegation six pointer.
“Jens and Kalvin going off was a blow,” McKenna said.
“They're still being assessed, to be honest. We don't know the severity, it looks like hopefully neither is a very, very serious injury, but they're still sort of getting some scans and assessments today before we know further. And other than that, I think we're similar to how we are.
“Of course, it will be nice to have Axel Tuanzebe back in the squad (following his one-match ban). Conor Chaplin’s got a full session in with the group today, which was good.
“Julio (Enciso)’s working with a physiotherapist still on his knee and otherwise, we're pretty much the same.”