N'Golo Kante is a doubt for Chelsea's game with Crystal Palace on Tuesday after suffering a hamstring injury in their win over Watford.
but their victory was marred by an injury to the French midfielder, who was withdrawn with 12 minutes remaining.
"N'golo has got a small hamstring (injury) which we'll have to scan tomorrow (Sunday) and see how bad it is," said Chelsea boss Lampard.
"We hope it's small, that's what I've been told so far. After the scan we'll know but I'm guessing it'll be a problem for Palace on Tuesday."
Chelsea's game at Selhurst Park is their first of three Premier League games in eight days. They travel to Sheffield United on July 11 before hosting Norwich three days later, with all three games live on Sky Sports.
Olivier Giroud, Willian and Ross Barkley found the net as Chelsea put their midweek loss to West Ham behind them with a routine win over Watford, which lifted them back above Manchester United into fourth place.