With Scott Kazmir's left elbow strain taking more time to recover from than initially expected, Shields will likely be the guy taking the ball when the Rays open the season against the Orioles in two weeks.
Shields, who signed a long-term deal in January that could last as long as seven years and be worth as much as $44 million with incentives, said being the Opening Day starter would be a meaningful achievement, particularly given a past that has seen him deal with career-threatening shoulder problems.
"It would feel great [to be the Opening Day starter], just knowing that the team has enough confidence in me to let me take Kaz's spot in that situation," Shields said. "And like I've always said, 'He's going to be the ace on the staff no matter what.' I'm just happy to take his spot. If it happens, I'm just fortunate enough they have a lot of confidence in me."
A conversation with Rays manager Joe Maddon -- which likely will take place Tuesday -- is the only thing separating Shields from officially being named the Opening Day starter.
"I would not [name him Opening Day starter] until I had a chance to speak to him about it first," said Maddon, who noted that even if Shields can figure it out, "it's appropriate to go through the proper channels."
Shields said he "definitely" feels for Kazmir because he's "been in his shoes" in having to overcome physical problems. But the 26-year-old right-hander hopes Kazmir will be patient and not rush to return, so that he can make a full recovery.
On Sunday against the Tigers, Shields struggled early in the early afternoon heat.
"Honestly, it wasn't my good stuff," Shields said. "It was just one of those days where you have to fight through with everything you've got. The heat kind of got to me at the beginning. And we've all been kind of sick around here. But I felt a lot better the last three innings, though."
Shields threw 39 pitches in the first two innings.
"My body was drained the first two innings, and I was trying to overthrow and overcompensate for my energy level," Shields said. "Last three innings, I toned that down a little bit and started throwing strikes."
Shields said Sunday's heat caught him off-guard.
"It surprised me, because I went out there earlier in the day and it wasn't that hot," Shields said. "But I've been kind of sick the last couple of days. And my body hasn't been feeling that good. So the heat and humidity got me the first few innings."
Shields retreated to the clubhouse in between innings a couple of times for relief.
"... [I] got some ice rubbed on my neck and stuff, cooled me down a little bit," Shields said. "[I] gathered myself up a little bit and the last few innings were pretty good."
Shields resembled the pitcher who went 12-8 with a 3.85 ERA in 2007 when he struck out Curtis Granderson swinging on three pitches to start the third inning, using his best pitch -- his changeup -- to finish off the Tigers' leadoff hitter. Shields threw 83 pitches and allowed no runs in 4 2/3 innings.
"He wasn't as sharp as normal in regard to location, but he got the appropriate number of pitches in and made some good pitches when he had to," Maddon said. "Once again, he demonstrates even when he's not at the top of his game, he pitches very well."
All in all, Sunday's effort served as a nice tune-up toward working Opening Day.
"If it happens, it happens," Shields said. "If it doesn't, it doesn't. [I'm] just trying to get my work in right now and get ready for nine innings during the season."
Bill Chastain is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.