But since arriving in Chicago, Hamels has delivered. And then some.
Heading into Tuesday's start against the New York Mets at Wrigley Field, Hamels has yet to lose as a member of the Cubs and is coming off an outing in which he delivered Chicago's first complete game of the season.
After struggling for much of the year with the Texas Rangers, Hamels is 4-0 with a 0.79 ERA in five starts with the Cubs. Hamels was 5-9 with a 4.72 ERA with Texas.
"To be a major league pitcher, you're going to have some tough times," Hamels told reporters after his win over the Cincinnati Reds, according to the Chicago Tribune. "You can't give in."
He added: "There are moments you have to earn it."
With the Cubs and Hamels rolling, the veteran left-hander will attempt to keep it going against the Mets. Hamels (9-9, 3.82) will be looking to help the Cubs extend their winning streak to six games after Monday night's 7-4 victory over the Mets.
Hamels is 9-14 with a 3.99 ERA in 32 career starts against the Mets but should have plenty of momentum given the groove he has been in since coming to Chicago. The change of scenery -- and playing for a contending team -- has worked wonders.
"When there's more at stake, you bring out the big guns. You dig down deep to who you are," Hamels told USA Today recently. "You don't hold anything back and you just let it fly. Who you are finally gets exposed out there to the public eye and to your teammates."
The Mets will attempt to bounce back from their second straight loss. A day after suffering a 15-0 setback to the Washington Nationals, the Mets couldn't hold a 3-1 lead and were done in by a two-run single by pitcher Jon Lester, who gave the Cubs the lead. Ben Zobrist snapped a 4-4 tie in the seventh inning with an RBI double.
On Tuesday, the Mets will counter with Jacob DeGrom, whose performance this year has been much better than his 8-8 record suggests. DeGrom touts a major league-best 1.71 ERA in 26 appearances this year and 174 innings pitched. He is coming off a tough-luck loss to the San Francisco Giants in which he allowed two runs (one earned) with 10 strikeouts. DeGrom is 2-2 with a 3.47 ERA in six career starts against the Cubs.
Despite often struggling to receive much run support from the Mets' offense, DeGrom has done his part to keep the team competitive. Between the lack of offensive help and having the bullpen implode after some of DeGrom's solid starts, he is stuck with the .500 record when his stuff has been good enough to make him a bona fide Cy Young contender if the Mets would have held up their end of the bargain.
Rather than getting wrapped up in hypotheticals, DeGrom instead focuses on himself.
"If you're the best you can be, you're going to help the team win," DeGrom said earlier this month, according to ESPN.com. "That's how I take it. I'm going to go out there and be the best that I can be and if I am, it's going to put us in pretty good position to win."