The Reds recorded a 5-0 victory over the Hornets to climb up to third in the Premier League table, but the win came at a cost with Can being forced off shortly before the half-hour mark due to a lower back injury.
However, Klopp does not believe that the problem will prevent Can from joining up with the Germany squad during the upcoming international break.
"[It is a] back [injury]. He doesn't think, and I don't think, it is too serious but it was too serious to continue," Klopp told reporters.
"He had that problem a little bit during the week; we gave him one day of extra recovery. But he thought it would work and he trained normally yesterday.
"It was one header and maybe because of the temperature in the muscle – it is a muscle thing. But it should not be that serious and he will go to the national team I think, and have their treatment. Their game is not tomorrow. Then we'll know more, but it should not be an issue."
Mohamed Salah scored four goals and set up another during the rout, taking him up to 36 goals across all competitions this season.