Last Tuesday's announcement that the Chicago Cubs had agreed to terms with ace lefty Jon Lester has now come to fruition. MLB.com's Carrie Muskat announced Saturday that the Cubs have officially finalized the contract upon Lester's passing of his physical exam. Lester will now officially begin earning his $155 million that he will receive over the next six seasons. The Cubs will hold a press conference Monday to formally make the announcement and introduce their newest ace.

#Cubs announce Monday news conference to introduce Jon Lester. It's official

— Carrie Muskat (@CarrieMuskat) December 13, 2014

Lester's contract means the Cubs will pay him an average of $25.8 million each year through 2020. 

Lester was CBS Sports.com's #2 costless agent pitcher before his agreement with the Cubs. His success in both the regular season (116-67, 3.58 ERA in nine years) and the postseason (6-4, 2.57 ERA in 14 games, 12 starts) were the main attractions for Cubs management to make such an extravagant offer. Muskat says that Oakland Athletics teammate Jason Hammel, who is returning to the Cubs after a July 6 trade sent him to Oakland, and fellow Athletics teammate Jeff Samardzija discussed pitching in Chicago with Lester, and those discussions may have helped "sell the left-hander on coming to Chicago."

In 2014, Lester was a combined 16-11 with a 2.46 ERA, 1.10 WHIP, and 4.6 WAR in 32 starts combined with the Boston Red Sox and Athletics. He will now head a rotation that also consists of Hammel, Jake Arrieta, and Kyle Hendricks in the first four spots. The fifth spot is currently up for grabs with Travis Wood, Tsuyoshi Wada, and Felix Doubront in competition for it barring any other moves in the rotation.

When Lester holds up his new Cubs jersey on Monday, fans will get to see what number he will wear. Lester wore #31 with both Boston and Oakland, but the Cubs have retired that number in honor of Hall-of-Fame pitchers Ferguson Jenkins and Greg Maddux.