St. Louis Cardinals ace Adam Wainwright will undergo an MRI on Monday to determine the severity of his lower leg injury, but sources say he will likely miss the rest of the season. Expect the Cole Hamels trade rumors to begin.

The loss of Wainwright will be a big one, but the Cardinals have dealt with him being out for a long period of time after he underwent Tommy John surgery and missed all of 2011. Additionally, they have starters Lance Lynn, Michael Wacha and Carlos Martinez who have all gotten off to good starts.

However, they now lack a true ace and may have problems in the near future filling Wainwright's spot in the rotation because starters Jaime Garcia and Marco Gonzales are dealing with injuries of their own. As a result, general manager John Mozeliak said prospects Tyler Lyons, Tim Cooney and Zach Petrick of Triple-A Memphis could be options, but he also said the club may explore other options.

"If you get into May and early June and you don't feel like the internal options are the solution you were hoping for then you might have to look outside," Mozeliak told Rick Hummel of the St. Louis Post-Dispatch.

"It's not too early to look outside but I don't think we necessarily have to do that yet."

Looking outside of the organization could mean doing their due diligence on Hamels, which is a move they've been linked to since the offseason. However, Bob Nightengale of USA Today tweeted on Sunday that the Cards "don't quite have the pieces to satisfy the Phillies for Hamels." It was previously reported St. Louis would need to part ways with Carlos Martinez to make a deal happen, but it's even more unlikely they'd be willing to do that at this point.

Instead, Bernie Miklasz of the Post-Dispatch suggests possibly striking a deal for a starter who will become a free agent after the season, including David Price, Jordan Zimmermann and Jeff Samardzija. Although that would be a good idea, the Detroit Tigers and Chicago White Sox are seemingly keen on signing Price and Samardzija to contract extensions while it's unlikely the Nationals would trade Zimmermann to a fellow postseason rival.

St. Louis is 12-5 and has a two-game lead in the NL Central, so it's likely Mozeliak won't rush to make a move. He has a capable cast of starters and probably wants to see how they perform sans Wainwright before deciding to make a drastic transaction.

We'll be keeping a close eye on the Cardinals, especially once Wainwright's MRI results are made known.