Despite opposition from a section of the Chelsea support regarding his appointment, Benitez confounded his critics by guiding the team to Europa League glory and a third-place finish in the Premier League.
Lampard, whose form under Benitez was rewarded with a one-year contract extension, admits the former Liverpool boss was thorough in his approach.
"He's a professional bloke. He prepared very well for games. And it was a difficult situation for him as well," Lampard said.
"As interim manager it was always going to be quite difficult because we all knew it was only to the end of the season.
"So there was no planning, no long-term relationships were going to be built. So, in that respect, he did a good job because we got the end result - success."
Despite that, though, Lampard did not grow close to Benitez on a personal level.
"There are certain managers you build relationships with and feel closer to," Lampard told The Sun. "He's not that kind of bloke.
"Other managers draw a bit of a line and keep it that way. Rafa's more like that.
"He was not really the sort of manager you could sit and talk with."