"I thought Cheltenham were terrific. It was a bit hard on them to lose like that," the Sunderland boss said after the game.
"They were well organised, well coached and it showed how difficult it is play when all 11 men are behind the ball.
"There were a few harsh words at half time before it had any effect but it's easier to go and play the likes of Chelsea at Stamford Bridge when the pressure is off.
"It wasn't pretty but we are in the next round and that's what matters.
"It wasn't a case of me resting players and I just hope the players who were out injured will be okay for Sunday's derby at Middlesbrough."