The former Anfield winger thinks Brendan Rodgers has made a "shrewd" signing in the former Southampton forward, who returned to his boyhood club in a fairytale move on Monday
The 32-year-old completed a dream move back to Merseyside on Monday, having formerly been released from Anfield as a youngster.
After five prolific years at the Saints, 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 his boyhood club for reported £4.5 million fee.
And former Liverpool winger McManaman thinks Brendan Rodgers has carried out a fine 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 The Mirror.
"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."
The transfer represents a significant profit on the £1m the Saints paid to Bristol Rovers to sign Lambert in 2009, a fee he quickly repaid by guiding the south coast club back to the top flight.
Lambert netted 106 goals in 207 league games during his time at St Mary's Stadium, and easily made the step up to the Premier League, scoring 15 times in his maiden campaign - a tally which made him the joint topscoring Englishman.
Former Anfield captain Jamie Carragher has also heralded the move, stating: "I think it's a very good signing. He's a local boy, a Liverpool fan, and it's probably been a dream for him."