As the Hornets prepare for a game against the Gunners on Sunday, they are sweating on the fitness of Cathcart.
With a new manager in charge at the club, Quique Sanchez Flores, Cathcart will have to wait to impress the Spaniard.
Flores spoke about present injuries with reporters and said: "We don't have many injuries," said Sanchez Flores.
"We have [Troy] Deeney and Cathcart, they're very important players, but when you don't have them, or you have some players with injuries, you need to accept that as soon as possible, you need to think about the person who is able to play.
"Craig has something in his muscle and I think it's something that will just keep him out for a short period."