Seeing a mob of reporters around his locker talking with Olsen, Willis grabbed two bats and placed them on the floor.
The bats were used to form a symbolic barrier between his and Olsen's locker. The gesture was greeted by laughter, as Willis walked away.
Returning a few minutes later, Willis again dealt with a huddle of reporters, only this time they were chatting with Sanchez.
Again being territorial, Willis simply switched the placement of the bats to the other side, gaining some more separation.
At 25, Willis is the veteran leader of a young pitching staff. He's also one of the league's most recognizable players.
With a 58-39 record, Willis already is the Marlins' career leader in wins.
If the Marlins are to contend for a playoff spot, Willis is expected to play a major role.
"He's special," new Marlins manager Fredi Gonzalez said. "He's a throwback-type player. He's like guys we read about: Satchel Paige, Sandy Koufax and those guys. Just the other day, he came out and threw a side [session]. It was cold and some of the Minor League players were out there taking batting practice.
"Willis came in, put a jacket on and came back out here and shagged [fly balls]. Nobody asked him to do that. This guy has been in the All-Star Game, he's played in the World [Baseball] Classic. That's him. Those are special guys."
A 22-game winner in 2005, Willis was 12-12 with a 3.87 ERA in 2006. At times he was a hard-luck starter, but he managed 223 1/3 innings, marking his second straight 200-plus-inning season.
In his second season of being arbitration-eligible, Willis has signed for $6.45 million, and he's eligible for free agency after the 2009 season.
The lefty has been community active and a positive role model since he broke in as a rookie in 2003. But in late December, two weeks after he got married, Willis encountered some legal trouble. He was charged with DUI near a South Beach nightclub.
The incident was the first blemish on his reputation, and he's determined to put that behind him and remain a positive influence.
"My teammates still believe in me," Willis said. "I'm still out here working. It's just another day. I never want to do anything to bring negativity to the ballclub or to my teammates or to myself. It was an unfortunate situation, and I moved past it. Now, I'm ready to work.
"Through baseball and through my teammates, I'm able to overcome that. I just pride myself [in doing] good things for people. My image is how you guys [media] portray me. I don't have a news camera or a microphone. I come here every day and take it for what it is."
Later Sunday morning, Willis threw off the mound for about 10 minutes. When his daily duties were over, he spent about 10 minutes signing autographs for fans waiting near the team parking lot.
"I'm going to continue to leave my heart on the field, and hopefully that's enough," Willis said. "I'm only going to do what I'm asked to do. I'm not going to go out there and try to be Superman and climb the fences. I'm going to sign autographs like I did the year before. I'm going to play hard like I did the year before, and hopefully that's enough."
Respected for his unrelenting work ethic and competitiveness, Willis exudes confidence that is so prevalent on the young Marlins.
Despite having the lowest payroll in the league, Willis feels the club has the makings of a contender. And in a rotation that includes second-year phenoms like Scott Olsen, Josh Johnson, Anibal Sanchez and Ricky Nolasco, the Marlins have the makings of one of the top pitching staffs in the game.
Asked about the rotation's potential, Willis responded: "The sky is the limit. I tell everybody that I'm the worst one out of this group. These guys are farther along than I was at that point."
The determination of the young pitchers was evident on Sunday morning when Sanchez headed to the weight room about 8:30 a.m., 15 minutes before a team meeting.
"I have respect for them and things they do off the field," Willis said. "Like Anibal going in there and working out before our meeting -- little things like that."
The talent of the staff has Willis confident that those pitchers won't fall victim to a "sophomore slump."
"I just believe you've got to go out there and play," Willis said. "I definitely think the media tries to embed that [sophomore slump] in people's heads. But I think you just have to go out there and play baseball. I told them to go out there and have fun."
An early observation from Willis is that Gonzalez and last year's manager, Joe Girardi, have similar objectives.
"Everybody wants us to work hard," Willis said of the new manager. "That's the common denominator. [Gonzalez] definitely wants to run a tight ship like Joe did. He wants us to work hard. I'm pretty easy as far as that goes."
When it comes to pitching, Willis compares his attitude to the title of a book by NFL wide receiver Keyshawn Johnson.
"I'm like Keyshawn: 'Just give me the ball.' You don't really have to say much to me, I'm willing to go out there and take the ball and have fun," Willis said.