Is Jon Lester really an ace?

The consensus is in: The Chicago Cubs are the big winners after signing Jon Lester to a six-year, $155 million contract that makes him the second-highest-paid pitcher on an annual average basis behind only Clayton Kershaw.

And the Boston Red Sox are the big losers, still left without a top-of-the-rotation starter among a group that includes Clay Buchholz (coming off a 5.34 ERA), Joe Kelly (coming off a 4.20 ERA), Rubby De La Rosa (coming off a 4.43 ERA) and not much else. Ruben Amaro's asking price for Cole Hamels just went up.

The consensus is the Red Sox blew it this past spring by offering Lester a mere $70 million over four years, when pitchers such as Hamels, Matt Cain and even Homer Bailey were receiving $100 million contracts. To be fair to the Red Sox, although Lester had a dominant postseason run in 2013 to lead Boston to a World Series title, he had been somewhat less than spectacular in 2012 and 2013 in the regular season, ranking 79th and 52nd in the majors in ERA among qualified starters those two seasons.

Here, Lester's ranks in various categories since he became a full-time starter in 2008 (including Baseball-Reference WAR and FanGraphs WAR):

You can understand Boston's reluctance to give Lester a Hamels-like $144 million contract. He wasn't one of the top 10 starters in the game at the time, and there was no indication that he deserved to be paid as the second-best starter in the game. Still, $70 million was a low offer, as Lester's peripherals suggested he was better than his raw ERA totals.

In 2014, Lester began throwing his cutter more often, which allowed him to pitch inside more to right-handed batters and made him much more effective against right-handers (he actually posted a reverse platoon split). He posted an ERA under 3.00 for the first time in his career (although that was helped by 16 unearned runs).

Lester was arguably a top-10 starter in the game from 2008 to 2010, although he never finished in the top 10 in ERA or in innings until ranking eighth in ERA in 2014. He wasn't a top-10 starter from 2011 to 2013. Yes, you can give him bonus points for his postseason history, but you might want to ask the A's whether past performance in October is a guarantee of future performance. For Lester to be worth $155 million, he has to not only stay healthy but maintain a level close to his 2014 performance.

Of course, it's not our money and, with so many low-paid youngsters in the lineup or ready to join the lineup, the Cubs had plenty of room in their payroll to invest in Lester. Even if the contract is an overpay in the end, if Lester continues churning out 200-inning seasons, the Cubs will be happy.

The Cubs are betting on continued good health and on the cutter pushing Lester to a new level as legit ace. With the cutter and the move to the National League and the easier lineups, I suspect Lester will reel off several outstanding seasons. Still, $155 million is a lot for a pitcher who hasn't necessarily proved himself to be a consistent No. 1 starter, let alone the second-best starter in the game.

The Cubs look like the big winners here, but there is another group of winners to consider: David Price, Jordan Zimmermann and Johnny Cueto -- free agents after 2015 and arguably better than Lester -- just saw their asking prices go way up.