The Baltimore Orioles are preparing for an absolutely massive four-game series against the Tampa Bay Rays this weekend, and they may have to do it without first basemen Ryan Mountcastle.

The 26-year-old is day-to-day with left shoulder discomfort after leaving Wednesday night's game following a first-inning foul ball, manager Brandon Hyde confirmed afterwards.

“I saw him wince after the foul ball,” Hyde said. “He's day-to-day right now. Hopefully, he's better tomorrow. I'm just not sure. Obviously, you don't want to lose anybody right now, especially Ryan.”

The O's open up a crucial set against their AL East rivals on Thursday night, in a series that could determine the winner of the division. It is the last time the two teams will meet this regular-season. Mountcastle opened up about the injury on Wednesday night.

“Took a swing, popped and just is what it is. I don't know what it is,” the slugger explained after the team's 1-0 loss to the St. Louis Cardinals.

“I just played a little defense, tried to take a swing in the cage and definitely, it wasn't ready to go. Not great, just got to get some imaging done tomorrow. Not sure what happened. It doesn't feel good, just praying for the best.”

It looks like Mountcastle could be in jeopardy of missing some, if not all of the weekend set at Camden Yards. He already missed a month with vertigo earlier this season.

Despite a phenomenal start from Kyle Gibson, the Orioles were unable to manage a single run against the lowly Cardinals on Wednesday. After losing two of three to the NL Central dwellers, Baltimore will open their series against the Rays just two games ahead for the AL East lead.

Still, they need just four wins to clinch a playoff spot, and it looks like the Maryland-based franchise will be back in the dance for the first time since 2016. The Orioles had won their previous seven series before faltering against St. Louis, and have still won seven of their past 10 games.

But the most crucial series of the season looms — and Ryan Mountcastle could be watching from the dugout.