TORONTO --- B.J. Upton got an unexpected start in center field on Saturday afternoon, and unfortunately for the Devil Rays, his inexperience at the position might have cost them a win.

In the bottom of the seventh inning, an aggressive baserunning move by Jays center fielder Vernon Wells caught Upton off guard. Wells took off from first base on the pitch, as Lyle Overbay singled softly to center. However, Wells never stopped running, rounding third base and trying to score. Instead of trying to make a play at the plate, Upton casually tossed the ball into second base, allowing Wells to cross the plate with what turned out to be the game-winning run. With the Rays' 5-4 loss to the Jays on Saturday afternoon at Rogers Centre, their record dropped to 14-22.

Tampa Bay manager Joe Maddon thinks the weird play simply was the result of having Upton play in center field for the first time.

"I think the assumption we made there was that [Wells] was going to stop at third base, and that's an experience issue," Maddon said. "Because if you know Wells and you know their third-base coach, [Brian Butterfield] is very aggressive in those moments. They got us."

Even though Wells was approximately 15 feet from third base when Upton got to the ball, Butterfield decided to take a risk because of Upton's lack of experience in the outfield.

"He's a guy that hasn't played out there a lot. He's still a very young guy," Butterfield said. "The direction the ball was hit, and Vernon off on the pitch, I knew he was going to be coming hard and expecting to go the extra base. It's Vernon Wells."

Prior to the game, Maddon got creative and unveiled a lineup that had Upton playing in center field for the first time in his Major League career. The 22-year-old worked on his defense at the position in Spring Training, but his only experience in the outfield at the Major League level came in left during the 2004 season.

"I told him last night [about the lineup change]," said Maddon prior to the game. "I wanted to see the look on his face [to see] if there was any kind of hesitancy. There was none."

Upton might not have hesitated when agreeing to play the position, but he did on the play in the seventh inning.

"He just has to unload that ball," Maddon said. "That ball has got to be unloaded and it's got to be back in the infield sooner, and he knows that."

Upton admitted after the game that experience may have played a factor, because he just wasn't expecting Wells to be that aggressive.

"I've never seen that play from center field," Upton said. "So, first time, and I'll know for next time."

Aside from that one play, Upton's defense looked pretty good in center. He made a strong throw to the plate earlier in the game, nearly tossing out Jays second baseman Aaron Hill, and he showed nice range on several of the fly balls hit his way.

Maddon said he wouldn't hesitate to use Upton in center again, because he feels Upton has all the physical skills to play the position well. It's just an experience Maddon thinks his young player can learn from.

"It's a teachable moment, and we'll discuss it with him in more detail," Maddon said. "But this young man has made a lot of progress already this year and I don't want anything to infiltrate his confidence in a negative way."

The disappointing finish to the game masks the fact that Tampa Bay starting pitcher Edwin Jackson (0-5) put forth a solid performance. The 23-year-old righty allowed four runs on six hits while striking out a career-high nine batters in six innings. It was the fourth time in his last five starts that Jackson has pitched at least six innings. Pitching deep into ballgames is something he has been concentrating on a lot lately.

"I'm just trying to string together some starts to keep my team in the game and see how many I can go," Jackson said. "[I'm trying to stay away from the crazy starts where I'm real erratic, all over the place. [I'm] just trying to stay consistent, win, lose or draw."

Jackson's biggest mistakes of the game came when he gave up home runs to Jays (15-21) left fielder Adam Lind and designated hitter Frank Thomas. Aside from those two pitches, though, Maddon thought Jackson showed a lot more poise than he has previously in pressure situations.

"I think in the past when things got hot, he had tended to just want to [throw] harder," Maddon said. "Most pitching coaches, and even good hitters, will tell you the best thing is to get softer. When hitters get amped up in certain situations, he's finding that he can get softer ... throwing sliders in a fastball count."

Left fielder Carl Crawford was the offensive star for the Devil Rays. In the top of the sixth inning, the 25-year-old took a 2-0 fastball from Jays starter Dustin McGowan over the wall in left for his sixth home run of the year. The blast all but ended the outing for McGowan, who surrendered four runs on seven hits in 5 2/3 innings.

Crawford is hitting .450 (9-for-20) with one home run, two RBIs and two doubles over his last five games.

Tampa Bay has dropped its last six games. On May 5, the Rays were just two games under .500, but their recent struggles have sent them to the bottom of the American League East standings. They currently are 10 1/2 games back of the Red Sox for first place in the division.

Slumps like this are bound to happen from time to time with a young ballclub like the Rays. Maddon thinks Tampa Bay can learn from plays like the one in the seventh inning, and use it to get better in the future.

"We're going to look back at this one day and realize there are growing pains involved when you get good," Maddon said. "When you're going through the actual growing pains, it's a little bit more difficult to see the lesson that potentially can be learned."