The 28-year-old left-hander has the fourth-worst ERA among qualifying American League starters. As the team's No. 1 starter, he's carrying a 5.46 ERA, making it no surprise that the Red Sox are at the .500 mark and in last place in the AL East.
All is not lost for Bobby Valentine and company, though.
It is all but a foregone conclusion that the Sox won't catch the New York Yankees, but they sit just 3.5 games out of the wild-card race with plenty of baseball left to play.
Lester, a two-time All-Star, surely didn't forget how to pitch overnight, but his poor performance over the last 11 times he has taken to bump tell a different story.
Since May 25, the ace of a beleaguered starting rotation boasts a stomach-churning ERA of 6.82 (stats are per Baseball Reference). The Red Sox are 3-8 over that span and opponents have posted a .318 batting average and a .932 OPS against a man that once threw a no-hitter.
The exclamation point on Lester's abysmal stretch was Sunday's four-inning, 11-run shellacking at the hands of the Toronto Blue Jays that saw nine hits, four home runs and five walks.
Lester is getting rocked. There's no disputing that.
His main problem is that he's falling behind in the count. Lester has fallen behind 1-0 to 212 hitters this season. After a 1-0 count, batters are hitting a robust .339 with 11 homers. When an at bat starts off bad for Lester, it isn't hard to tell that it's going to get worse.
When Lester throws a first-pitch strike, opponents are hitting a far more respectable .240 for the rest of the at-bat.
Boston's circus-like season seems to be having an impact on Lester's psyche. According to NESN's Didier Morais, Lester had this to say following the worst outing of his career:
It's embarrassing. I've let my team down a lot this year. It's hard for me to walk around this clubhouse and look guys in the eye right now. I'm not pitching well. I'm not doing my job. Guys scored seven runs today, we should win that game.
Any pitcher would be thinking that, but we seldom see one come out and say it.
According to Fan Graphs, Lester is using his cutter on 11.2 percent less of his pitches than he did last season when he went 15-9 with a 3.46 ERA. He's using his fastball nearly seven percent more and his changeup almost five percent less.
Those numbers aren't drastic, but it would be wise for the Red Sox coaching staff to attempt to get Lester to return to what made him great in years past.
About 18 months ago, ESPN's Buster Olney wrote an article detailing which pitchers had the best statistics when throwing a specific pitch. Of pitchers that threw at least 100 cutters, hitters accumulated a mere .166 average against Lester, the lowest in the AL for the 2010 season.
Just to put that number in perspective, it is eight percentage points lower than what Mariano Rivera posted—and we all know who supposedly has the best cutter in the game.
Lester also made the best curveball list after posting a batting average against of just .136 when he broke out Uncle Charlie.
Those numbers are from awhile back, but Lester was nearly as good then as he was at any time in his career. To stray from his past approach is to ask for trouble.
Some would argue differently, but the statistics point to Lester's overuse of his fastball contributing to his problems. When off-speed pitches aren't worked in efficiently, major league hitters have no problem sitting dead-red on Lester's low-90s heater.
The Sox are fortunate to be 48-48 this year, and it is all thanks to their potent lineup. They are first in runs scored, sixth in batting average, 10th in on-base percentage and fourth in slugging.
How many games will the Red Sox win this season?
This has all happened largely without Jacoby Ellsbury, completely without Carl Crawford and in the absence of Adrian Gonzalez's power stroke. Luckily for the Red Sox, Ellsbury and Crawford have returned and A-Gon is hitting .406 in July with three long balls in his last seven games.
All of the run production will be in vain if Lester does not get better quickly. Josh Beckett has been nearly as bad, and if Lester doesn't right the ship, the Red Sox have no shot at making a second-half run at postseason play.
As the ace, Lester is supposed to be the stopper. If the Red Sox are on a four-game losing streak, he's supposed to come in on the fifth day and give his team the feeling that a win is on the way. That couldn't be farther from the truth this season, and that must be fixed.
If it isn't, the Red Sox will fall into non-contender obscurity soon enough.