Gaston Ramirez and Jos Hooiveld's late header to secure safe progression and a 2-0 win, with assistant manager Perez quick to praise tonight's opposition after the game.
"We were obviously made hard to work in the second half," said the Spaniard, speaking instead of manager Mauricio Pochettino. "I thought the game was difficult.
"We scored in the first half but the opponent played well. They played without pressure.
"We are very happy about the result because it became a hard training session towards the end of the game.
"We know it is difficult to play as a team when you've made 11 changes, but this type of game, the cup games, we have to fix these kind of problems.
"We know it is not for the players playing the best football."