Toronto's right-hander was forced to leave a Minor League game during the second inning on Sunday afternoon with pain in his foot. He was later examined by podiatrist Dr. Glenn Copeland and received the preliminary diagnosis.
McGowan is listed as day to day and will need to be re-evaluated on Monday, but the club is optimistic this isn't going to be a long-term problem.
"It's day to day, which means it's shorter term, so we don't believe it's going to be that long," Blue Jays general manager Alex Anthopoulos said.
"I wouldn't make it that big of a deal. It's literally day to day. If we knew right now it was going to be weeks or months, we'd say that. I know it's a story, but I would not jump the gun on this and blow it out of proportion. If it ends up being a long time, or something was to change, I understand, but that's not the plan at all."
McGowan had been considered the clear-cut favorite to win the final spot in Toronto's starting rotation, but there's competition from left-hander Aaron Laffey and right-hander Kyle Drabek.
McGowan was projected to make his first start of the regular season on either April 10 or 11 vs. Boston. He was set for three more outings before the end of the spring. Those starts in Florida would have been used to continue building arm strength.
McGowan was scheduled to throw five innings and approximately 75 pitches on Sunday, but he ended up tossing approximately 20. He'll still have time to get stretched out if he doesn't have to miss his next start, but at this point, that seems questionable.
"It all depends -- if he comes in tomorrow and he doesn't feel a thing, pain-free, everything's fine, sure. But I'm not expecting that," Anthopoulos said when asked if McGowan could still open the year as the No. 5 starter.
"... Sounds it's going to be better, but it might be a day or two of not throwing and then should be OK. Today, it's all going to be dependant on how he feels. We're not going to take a chance and move too fast with him, but if he's 100 percent three days from now, we'll get him back on track."
Plantar fasciitis is the inflammation of the connective tissue that begins at the heel of the foot and extends towards the sole. It can be very painful and often becomes a nagging problem that is difficult to treat.
It's the same ailment that former Toronto outfielder Scott Podsednik experienced last spring. The difference between the two, according to Anthopoulos, is that Podsednik's connective tissue was completely torn and McGowan's is just inflamed, which should help ease the recovery process.
McGowan didn't speak to reporters on Sunday afternoon. The native of Savannah, Georgia, made his return to the Major Leagues last September following a three-year absence following two major shoulder surgeries and one knee surgery.
He was healthy and appeared on his way to cracking Toronto's rotation this spring. Now, McGowan's status for the regular season will depend on just how quickly he can get back on the mound.
"We're never going to quit on this guy," Anthopoulos said. "From that standpoint, we're going to be there, and if he's on track, he's on track. If he's delayed a few days, we'll just adjust accordingly, but there's two weeks or so left in Spring Training, and we have time to see where things stand and develop."
If McGowan is unable to go, that would open the door for either Laffey or Drabek. Laffey got his opportunity to impress the Blue Jays on Sunday against Boston, but he surrendered five runs on nine hits in five innings.
Laffey is doing his best to focus on the task at hand with just nine days remaining in camp.
"From the time I broke in, I've been coming into a situation every year battling for a job, fighting for a job," said Laffey, who has a career 4.34 ERA in parts of five seasons. "Starting all the way back in '08, I was competing for a job against Cliff Lee, and then he goes off and wins a Cy Young.
"Injuries happen, they occur, they're a part of the game. Guys underperform, and that's part of the game -- that's the nature of the beast. ... It kind of has become just second nature to have that tunnel vision."