By Bruce Levine-

(CBS) — Cubs starter Edwin Jackson took the weight of the baseball world off of his shoulders by admitting he has been pitching with a sore lateral muscle the last two weeks.

After having the worst starting record in baseball over the past two seasons, Jackson was put on the 15-day disabled list Thursday. He is a combined 14-32 with a 5.47 ERA in his two seasons in Chicago.

The veteran starter was awarded a four-year, $52-million contract before the 2013 season. That contract will expire after the 2016 season. The Cubs’ brain trust believed Jackson could help supply stability and provide innings for a rotation full of unproven young pitchers. That theory has proved to be wrong for both the team and the pitcher.

What has eased the pain for the Cubs is the professional way Jackson continues to comport himself. Normally a player will lose his composure or turn on coaches or other teammates when things go bad. In the case of Jackson, the worse he pitches, the better he gets in the clubhouse.

Jackson points to his parents and the “no-excuse” upbringing he had as a child.

“I have never been one to make any excuses,” Jackson said Thursday. “I don’t say anything to anyone I got out, knowing I have a job to do. Once you choose to take the field, you choose to handle anything that comes along with it.”

Wednesday night’s start was the last straw for Jackson, as he allowed seven runs in two-plus innings of work.

“Clearly, I know I can’t pitch now the way I can,” Jackson said. “I haven’t made any complaints about anything going on with my body. As a professional, you go out there and don’t live with any excuses. It got to a point where you battle, battle, battle until you decide you have to do what is best for you and the team.”

Jackson wants to get back on the mound before the end of the season to begin the process of becoming a rotation contributor once again.

“I really want to get back in September,” he said. “I really don’t feel like this will be a season-ending injury. That is part of the point of coming to this conclusion, that it would not turn into a season-ending injury.”

The 30-year-old Jackson has pitched in two World Series and one All-Star Game. Jackson has pitched for eight teams in his 11-year major league career, which he started as a 19-year-old in 2003.

Right-handed Jacob Turner will most likely move into Jackson’s rotation slot when he has built up enough innings.

Bruce Levine covers the Cubs and White Sox for 670 The Score and Follow him on Twitter @MLBBruceLevine.

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