The Kansas City Royals thought so much of young catcher Salvador Perez that they recently signed him to a five-year contract extension worth $7 million, even though he had played just 39 major league games prior to this season.

Now, the Royals have cause for worry about Perez. Bob Dutton:

Perez suffered a still-unspecified knee injury before a 7-5 victory over the Cincinnati Reds while warming up starting pitcher Jonathan Sánchez in the bullpen at Surprise Stadium.

"I don’t really know what happened," manager Ned Yost said Tuesday in his post-game news conference. "He was down in the pen, and he came back and said he tweaked his knee.

"They checked it (on the bench). It was sore, but he could crouch. He went out for the first inning and came back in, and Nick (trainer Nick Kenney) said he wanted to take him up and check him. That’s the last I’ve heard."

Perez caught the first inning of the game against the Reds before departing for Cody Clark. He sent a message through his own Twitter account that he's headed to Kansas City for further tests:

Heading to KC today -- Thanks to all the fans for the support . I will work hard to be back as soon as possible - God bless you

— Salvador Perez (@SalvadorPerez15) March 14, 2012

The Royals earlier this spring lost catcher Manuel Piña, also to a knee injury, and have only one other catcher (Brayan Pena) on their 40-man roster.