Watford manager Javi Gracia admits his side are "paying for mistakes" after they were beaten 2-1 at Birmingham City.
Othmane Maamma halved the deficit for the Hornets in the second half after Paik Seung-ho and Demarai Gray put the Blues in front at half time.
Gracia was left frustrated by errors costing the Hornets an "equal" game.
"We knew before coming today would be a tough game," he told BBC Three Counties Radio.
"In my opinion, it was equal. In the first half, they dominated more than us but we both had good chances.