Mileta Rajovic and Tom Dele-Bashiru spared Watford blushes as the Hornets edged to a 2-1 FA Cup third-round victory over Chesterfield.
Defeat was a cruel blow for the non-league side, who deserved at least a replay against their higher-placed opponents
The Championship side gave a first start to Rhys Healey, while Chesterfield made five changes - Liam Mandeville, Ryheem Sheckleford, Joe Quigley, Ollie Banks and goalkeeper Ryan Boot coming in for the National League leaders.
Watford almost took a fifth-minute lead when Yaser Asprilla intercepted a back pass from Branden Horton, but his effort was blocked by Sheckleford.