The 32-year-old completed a dream move back to Merseyside on Monday, having been released from the club as a youngster.
After five prolific years at Southampton, where Lambert's goals helped the south-coast club climb from League One to the top half of the Premier League, the England international joined Liverpool for a fee believed to be in the region of £4million.
And former Liverpool winger McManaman thinks Brendan Rodgers has carried out a great piece of business in capturing the striker.
"If he can replicate those kind of (goalscoring) figures for Liverpool I think they got themselves a really shrewd bargain," he told TheMirror.
"As we know football isn't about four-year signings or five-year signings, it's about next year.
"It's year to year unfortunately. It's a wonderful opportunity for Rickie."
