In eight appearances this season, Thatcher has a 1.29 ERA.
"Just attacking the strike zone," Thatcher said. "Making pitches, going after guys."
As for his struggles last year, Thatcher said he never lost faith in his ability.
"That wasn't who I was," he said, adding that after going through Spring Training with the D-backs, he now feels more a part of the team than he did last year.
So far, Thatcher has even been effective against right-handers, holding them to two hits in 12 at-bats.
Steve Gilbert is a reporter for MLB.com. Follow him on Twitter @SteveGilbertMLB. This story was not subject to the approval of Major League Baseball or its clubs.