Frank Lampard believes Chelsea begun to play better after Manchester United changed to their regular formation in the FA Cup semi-final on Sunday.
Both sides lined up in a three-at-the-back formation - the same system United used in their two wins at Stamford Bridge earlier in the season.
However, Ole Gunnar Solskjaer opted to change his tactics with half-time approaching following a serious injury to Eric Bailly. The Ivorian clashed heads with teammate Harry Maguire and was forced off the field on a stretcher while wearing a neck brace.
Anthony Martial replaced the defender as United shifted to the 4-3-3 formation that has worked brilliantly since the restart of the Premier League. Moments later, Olivier Giroud opened the scoring before Mason Mount and an own goal from Maguire in the second half booked Chelsea's place in the final.
Lampard admitted he was surprised that he felt his side should have scored even more.
"I can't ask for anything more than that - maybe a few more goals which is surprising when you play against a team of their quality," he told BBC Sport .
"We played with a system that we haven't played with in a while and I was surprised that they matched us up before (in the Carabao Cup and league meetings in October and February respectively).
"But in the early parts of the game I thought we were on top but when they changed the system I think we played even better. We did everything that I asked of them.
"I'm very proud of the performance."
