Pitching coach Ray Searage and manager Clint Hurdle advance several theories to explain the transformation, from pace to a growing reliance on his sharp changeup, and everything in between.
Really, however, it boils down to one thing: Locke has learned to trust his stuff.
"I'm trying to limit the walks as much as I can. Last season," Locke said, "it was the other way around: Limit the runs. If I walked them, it was no big deal, just don't let them score."
Keeping teams off the scoreboard is the ultimate objective, sure. The difference in Locke's new approach is it allows him to pitch deeper in games. He has already worked into the eighth inning four times, something he had never done before this season.
"That was the other goal this year, to go deeper," Locke said. "I'm getting ahead [in the count] and forcing them to swing, and guys are making plays behind me."
Asked for his own reaction when he looks at his walks column, Locke grinned and said, "I'm happy about it." And he probably has to take a second look, too.
Tom Singer is a reporter for MLB.com and writes an MLBlog Change for a Nickel. He can also be found on Twitter @Tom_Singer. This story was not subject to the approval of Major League Baseball or its clubs.