Worley wound up walking Fowler to extend the third inning, and the heart of the Cubs' lineup tacked on three runs as the Pirates lost, 4-0, at Wrigley Field.
"After the two-out walk, Vance wasn't able to execute pitches that he's been able to execute throughout the young season so far," Pirates manager Clint Hurdle said.
Worley said he thought Fowler was "just barely getting" to his fastball, so he decided to mix things up and try to sneak a backdoor cutter over the plate.
"That one didn't quite break over as much as I would've liked," Worley said.
Cubs right fielder Jorge Soler then knocked a single to right to put runners on the corners. First baseman Anthony Rizzo followed with an RBI double to center, and Kris Bryant put the finishing touches on the rally with a two-run single to center.
"We had trouble putting away the third out in that inning, but they took what they were given," Hurdle said. "They weren't big swings."
Worley allowed only one more run after that -- in the fifth inning, also with two outs -- and left following six innings of work.
"All in all, it's not a bad outing by any means," Hurdle said.
But it wasn't enough to keep the Bucs' five-game winning streak alive, as they were shut out for eight innings by Cubs right-hander Jason Hammel.
The Pirates managed only four hits, all of them singles, including one by Worley, his first hit of the season. The Bucs only had one at-bat with runners in scoring position, and Worley helped set it up with a one-out sacrifice bunt in the fifth inning.
"He was aggressive, attacked the zone," Hurdle said of Hammel. "First-pitch strikes, hitters retired in three pitches or less, aggressive, down, good sinker with some steam behind it. ... He controlled bat speed all night long."
In short, Hurdle pointed out afterward, Hammel put together the kind of start the Pirates just rode to five straight wins.
But with the Pirates' bats quieted Monday, one pitch was enough to let the Cubs end the Bucs' streak.
"All you can do is attack and hope that the ball eventually finds somebody," Worley said. "It took a few batters more than I would have liked, but I got out of it and gave the team a chance."
Adam Berry is a reporter for MLB.com. Follow him on Twitter at @adamdberry. This story was not subject to the approval of Major League Baseball or its clubs.