Di Matteo, who was promoted from assistant to interim manager, has guided the Blues to an FA Cup semi-final showdown with Tottenham.

The west Londoners are also in the driver's seat to clinch a Champions League semi-final place after knocking Napoli out in the last 16 and grabbing an impressive first-leg quarter-final away win at Benfica.

And Lampard feels that recent success is a result of new-found confidence instilled by Di Matteo.

"It's simple, not over-complicated," Lampard told BBC Radio 5Live.

"It was a case of getting confidence back in the team. Judging by the results, in majority, he's done that.

"The roles are different (assistant and manager). I think it's brought out a lot in him, being manager.

"He's been a manager before - successfully with MK Dons and West Brom. When he left West Brom people weren't sure (about the decision) - they probably would have stayed up anyway. I think he's revelling in making decisions."

The Blues are currently fifth place in the Premier League, five points behind Spurs who sit in the fourth and final Champions League place.

Lampard, however, refused to blame Villas-Boas for Chelsea's poor results in the league, and feels that it was low confidence within the team that saw the Portuguese sacked.

"We didn't perform to a level and that's why there was a change in manager and that's why as players we weren't happy," he said.

"There's a lot to be said of having a confident squad. It seems like we're in a better position now than we were in the past.

"There are too many reasons (for why we were not performing well) rather than one special thing."

During Villas-Boas' nine-month reign the Blues midfielder found himself pushed out of the starting XI, and although he has been reinstated under Di Matteo, the 33-year-old was left on the bench for Chelsea's midweek victory at the Estadio da Luz.

However, the Englishman felt the Italian's handling of his omission was different to that of Villas-Boas' in Chelsea's last-16 tie away at Napoli.

"It's fair to say (there was difference in approach about being told he was not starting against Benfica and Napoli)," he said.

"Different managers have different ideas. I spoke to Robbie (Di Matteo) before the (Benfica) game. There was certainly no issue."