Doolittle's run is second all-time among Oakland pitchers, behind the 50 1/3 walk-free innings thrown by legendary closer Dennis Eckersley between Aug. 17, 1989, and June 12, 1990.
Doolittle has not walked a batter since last Aug. 31. The hard-throwing lefty is pitching with swagger, but he leaves it in his locker every night.
"I've got a lot of confidence, right now," Doolittle said. "I've learned in my time in the big leagues as a reliever, stuff can change in a heartbeat."
Doolittle lives and dies by his fastball. Lately, with his ability to move the fastball, he has been living it up.
"I feel like with the way I have been able to command my fastball -- especially recently -- I can get ahead and expand from there, get some swings outside the zone," Doolittle said. "That's been the biggest thing, go 0-1, then take it one pitch at a time from there."
Doolittle was converted from a first baseman to a pitcher late in the 2011 season, and knowing how hitters think has shaped his aggressive pitching style.
"Kind of having that experience as a hitter, I know it makes such a difference when you step into a [batter's] box and then you're behind 0-1 or the count's 0-2," Doolittle said.
Doolittle has struck out 15 batters in his last 9 1/3 innings. His success is all about execution, not late-inning mystique.
"They know what I'm going to do, as far as attacking with the fastball and moving it around the zone," Doolittle said. "They know what I'm going to do. I don't think it would be particularly intimidating."
Stephen Ellsesser is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.