Those who have gotten to know Oswalt over time have a different impression. He's bright, engaging and quite animated when he feels strongly about a topic.
Count opposing players as a group that fits into the first category. Oswalt is old school when it comes to fraternizing with the opposition -- in other words, he doesn't do it. He sees no reason to buddy up to a bunch of hitters he's trying to beat the next day.
But Oswalt makes exceptions from time to time. He has developed friendships with select pitchers from other teams, including Padres ace Jake Peavy, whom the Astros will face on Opening Day on Monday in San Diego.
Oswalt, the only star pitcher on this year's Houston staff, will also take the hill at PETCO Park in his club-record sixth straight Opening Day start. He and Peavy, who forged a friendship after meeting at the All-Star Game in Detroit in 2005, are looking forward to the matchup. They've exchanged light-hearted trash talk ever since the 2008 schedules, released last year, revealed the Astros and Padres will open the season together.
"He said he's ready," Oswalt said with a grin.
And Oswalt's ready as well. Question marks pepper the rest of the rotation, Nos. 2-5, but the one constant is Oswalt, who leads all pitchers with 112 wins since he broke into the big leagues in 2001. Since 2004, he's second in all of baseball with 69 victories, behind only Johan Santana, who has 70.
The Astros have a daunting task on Opening Day as well. They'll face last year's best National League pitcher, one who grabbed the pitcher's version of the Triple Crown, and was only the 12th pitcher in NL history to win the Cy Young Award with a unanimous vote.
Peavy is also a hunting aficionado, and that hobby sparked the friendship with Oswalt. The two met three times last offseason to hunt -- once in Illinois, once in Oswalt's hometown of Weir, Miss., and once on Peavy's turf near Mobile, Ala.
The Opening Day matchup probably came up in conversation, but Oswalt, driven by his fierce competitive streak, guaranteed friendship will take a backseat once they step onto the field.
"It'll get real serious once we cross the lines," Oswalt said. "Maybe there will be a little smile if I hit a bomb off him or he hits a bomb off me. But it'll be all business once we get on the field."
It's anyone's guess how the Astros will fare this year, but the 30-year-old Oswalt could be in for a fruitful 2008 campaign. A revamped lineup gives Oswalt a comfort level he hasn't had in years, and the projected extra run support could mean a third 20-win season for the Astros' ace right-hander.
"It is a great feeling when you have a big horse like that, that you can run out there and you've got really a great chance to win that day. When he's really on, you're almost guaranteed a win. He's a big-time player."
Opening Day honors are hyped by fans and media, but Oswalt isn't one to get caught up in the hoopla. Although he'll set a record when he opens the season with the Astros for the sixth consecutive year, he still doesn't see what the big deal is. Especially considering the Astros are opening the season on the road, a rare occurrence for a team that plays in a warm climate with a roofed stadium.
"It's a lot better when it's at home, in front of your home field," Oswalt said. "But the opening of the season is great, because it means Spring Training is over."
Alyson Footer is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.