When assessing his 2007 season, the 24-year-old doesn't like what he sees. His record was 10-15 with a 5.81 ERA, including 133 strikeouts and 85 walks in 176 2/3 innings.
"Not good at all," Olsen said. "I think they're a little bit misleading. I think the ERA was not as bad as it looked. Certain games were obviously pretty bad. Other games were not.
"Overall, they were below average. I don't think I'm a below-average pitcher. I think it was a combination of things [that] led to that."
The Marlins are certainly counting on vast improvements from the brash left-hander, projected to be the Opening Day starter on March 31 against the Mets at Dolphin Stadium.
But Olsen, who has made more than 30 starts in each of the past two seasons, is now dealing with a minor physical setback, having recently experienced a bout of tendinitis in his left shoulder. Though the condition is not believed serious, any blip in routine may affect where Olsen slots into the rotation when the regular season begins.
Before Olsen came down with a sore shoulder, the Marlins liked what they saw in him.
"Until he took a little time off, he directed himself really good," pitching coach Mark Wiley said. "His fastball command has been much better. That's one of our goals for him this spring. I think we can get him back in there pretty much up to speed. We're going to be cautious and make sure he's 100 percent, and we'll go from there."
Last season Olsen took the mound in the second game of the season behind former team ace Dontrelle Willis, who has since been traded to Detroit.
A few years ago, Olsen had a reputation for being one of the best left-handed pitching prospects in the game. As were so many on the young Marlins squad, he was placed on the big league fast track.
In 2006, Olsen was one of more than 20 rookies to play for Florida. He enjoyed a solid first big league campaign, going 12-10 with a 4.04 ERA. In 180 2/3 innings, he struck out 166 while walking 75.
An up-close look at the club as we approach Opening Day
So why the sophomore slump?
"Last year we struggled a lot with fastball location," Olsen said. "We struggled a lot with my off-speed pitches when I was behind in the count. I had a lot of walks because of that."
Now that Willis is gone, Olsen is being counted on to assume a big role in a rotation that remains unsettled as Spring Training is about to head down the home stretch.
Injuries ravaged the rotation a year ago, putting extra pressure on Olsen and Willis to perform. But both had struggles of their own, thus the pitching never lined up and Florida finished in last place with a 71-91 record.
Marlins starters logged the second-fewest innings of any team in the National League in 2007, compiling 856. And for the first time in franchise history, no Florida starter posted a complete game in a season.
It's no secret that Olsen wants the ball on Opening Day. He's lobbied for it since Willis was dealt.
"It would mean a lot," he said. "Maybe the manager looks at you as if you are going to be that stopper. If you get on a losing streak, and if they need somebody to go out there and give you that quality start, you are looked upon as the guy who can do that."
Overall, 2007 was a rough year for Olsen, who encountered trouble both on and off the field. While enduring a topsy-turvy season, he was confronted with a legal problem stemming from DUI and other criminal charges.
Those issues now are behind him, and he's ready to regroup for his third season.
"They say the third year is a big year for any player," he said. "So personally, I just want to improve on the aspects of the game that I haven't been doing well at, especially last year. Obviously, if I can correct some of those things, my walks will go down. That's the biggest thing -- not putting guys on base."
Olsen also recognizes the importance of focusing on the inner workings of the game. He points out that established veterans, such as John Smoltz, Tom Glavine and Greg Maddux, make adjustments quickly.
"That's a huge step for any pitcher to make," Olsen said.
His passion for competition carries over to his personal life. In his free time, he enjoys watching TV game shows. His favorites include "Deal or No Deal," "Are You Smarter Than a 5th Grader?" "Jeopardy!" and "The Price Is Right."
"I like seeing people on game shows," he said. "I don't know why. It's like an up-and-down roller coaster ride for them. They might win money, and they might lose money. It's entertaining to watch people's actions.
"'Deal or No Deal,' that's the best one on TV right now. I'd love to be on a show. That would be hilarious."
Asked how he and some of his teammates would do in a "Jeopardy!" celebrity tournament, he responded, "I don't know how we'd do. A lot of us didn't go to college.
"Some of those decisions I see people make on those shows, I don't know if I could make them," he added. "Most of those people aren't as blessed to play baseball like me. It's a little bit [of a] different situation for them than it would be for me. If I were on a game show, I'd be playing for charity."
Joe Frisaro is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.