Taking the mound a day after Stephen Strasburg made his Arizona Fall League debut, Simmons tossed three shutout innings Saturday as the Phoenix Desert Dogs handed the Surprise Rafters their first loss, 11-2.
Simmons (1-0) began his second AFL stint by allowing two singles and two walks while striking out three.
"I hadn't thrown to hitters in a real game since the end of August. Being back on the mound, it felt great," the Athletics prospect said. "I had some success today, so it's definitely a confidence-booster."
Selected by Oakland with the 26th overall pick in the 2006 Draft, Simmons went 7-7 with a 5.72 ERA in 23 games at Triple-A Sacramento. He pitched in the 2007 Rising Stars Showcase and is back in the AFL after spending three weeks in August on the disabled list with a strained right deltoid muscle.
"I missed three or four starts. I didn't get the amount of innings the organization would like to see me get," Simmons said. "I'd strung together quite a few good starts. The last thing you want to do is get injured when you're throwing well. I knew we had a shot at the playoffs, so it was hard for me to go through that."
Simmons also is trying to develop an "out pitch."
"It seems like I can get two strikes on everybody," the 23-year-old right-hander said. "I'm working on a cutter and throwing the curveball a little harder. The last two years, it's been a little loopy."
Josh Wilkie (Nationals) worked two innings and Hiroshi Katayama, Heath Rollins (Rays) and Jeff Mandel (Nats) kept the shutout intact until the ninth, when Surprise (4-1) scored twice against A's farmhand Sam Demel.
Former first-rounder Brandon Snyder (Orioles) gave Phoenix (4-1) a quick lead with an RBI single in the first. A two-run homer by Blue Jays prospect A.J. Jimenez highlighted the Desert Dogs' five-run fifth and Snyder had another RBI single in a five-run ninth.
Cardinals Minor Leaguer Mike Parisi (0-1) got the loss, despite yielding a run on four hits in four innings.
Jeff Bianchi, Kansas City's second-round pick in the 2005 Draft, went 3-for-4 with an RBI for the Rafters.
Daren Smith is an editor for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.