Young starters Mason Mount, Billy Gilmour and Reece James were sent to the bench for goalscorer Ross Barkley, Mateo Kovacic and Cesar Azpilicueta.
After the 1-0 win booked them a Wembley date against Manchester United next month, Lampard said: “We haven’t played that badly since I’ve been back, we were fortunate at halftime that it was 0-0.
“We got lucky today.”
Of the three youngsters, he adds: “It is a learning experience. I could have taken more off, or other players off. I am not pulling those out on their own. They will be top players for this club and have top careers.
“But if I have to do something in games I will do it. It was one of those games where I had to do something.”