He hasn't felt that emptiness this early in October since the Astros last missed the playoffs in 2003. Oswalt certainly gave his club a chance to return to the postseason this season with a 15-8 record, a league-leading 2.98 ERA and 166 strikeouts.
Unfortunately, the Astros came up just short despite a September stretch run for the ages. Oswalt's performance during the past month was just as memorable, and, as a result, he was named the National League's Pitcher of the Month for September.
Without Oswalt, the Astros wouldn't have put as much heat on the Cardinals as they did in September. He went 5-0 with a 1.85 ERA and 39 strikeouts over six starts during the month. The Astros really didn't have any postseason hopes midway through the month, but outings like Oswalt's gave them something to play for.
"Not only would we not be where we're at without him, he's our horse," Astros reliever Russ Springer said. "What he means on this team cannot be measured."
Oswalt means more than wins and losses to the Astros. He's their big-game pitcher, even with Roger Clemens and Andy Pettitte behind him. Besides, his record this season doesn't do Oswalt justice anyway.
"The bullpen's blown a lot of his wins," Astros reliever Brad Lidge said. "He could have a lot more."
Oswalt made seven quality starts that resulted in no-decisions this season. If only a few of those were victories, he could have been a runaway winner for the Cy Young Award.
Still, his performance in September makes him one of the league's best candidates for it.
"Roy's not making a salary drive -- he already did that," said manager Phil Garner, referring to Oswalt's brand-new five-year contract extension. "So he must be making an awards drive here. He's come on strong. He's been absolutely golden for us."
Oswalt was great even when a muscle spasm in his neck bothered him Sept. 18 against the Reds. He felt the spasm early during that outing, but he completed 6 2/3 innings, allowed two runs and picked up his 14th win.
"He's one of those rare people -- and we have a couple of them here -- who has good stuff every time he goes out," Garner said. "I've seen a few of them over the years. I think back on Catfish Hunter, Steve Carlton. Steve Rogers was that way -- always had electric stuff."
Like Rogers, Oswalt's never won a Cy Young Award. But perhaps his perfect September was exactly what he needed to earn that honor.
Kevin Yanik is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.