KANSAS CITY -- The Royals¡¯ offensive outburst to begin Monday afternoon¡¯s game against the White Sox quickly turned to concern an inning later when first baseman Vinnie Pasquantino injured himself on a swing that resulted in a flyout in the second inning at Kauffman Stadium.

On an 0-2 count against White Sox reliever Vince Velasquez, Pasquantino swung at a slider on the inside part of the plate and grimaced right away while hunched over in pain as the ball traveled to center field.

The Royals announced that Pasquantino left the game with right shoulder discomfort, and he landed on the 10-day injured list Tuesday with the same diagnosis. The club recalled catcher Sebastian Rivero from Double-A Northwest Arkansas to give them a third catcher.

Pasquantino will continue to be evaluated, but the Royals are hopeful the IL stint is not a long one, perhaps allowing him to return after 10 days (the minimum number of days required of a position player after being placed on the IL).

¡°Trying to do anything before [10 days] would have been a push,¡± manager Mike Matheny said. ¡°We¡¯re still learning Vinnie as an athlete, how his body responds, and especially with these younger players, we¡¯re going to err on the side of caution. We knew it was going to take some time just to calm down.

¡°He¡¯s been in a really good place as far as his swing goes, and we don¡¯t want him to compromise that right now. Let¡¯s make sure we¡¯re taking the time, that he does everything to make the medical team feel really confident that he¡¯ll jump right back in the box next time and not have any hesitation at all.¡±

The Royals¡¯ rookie cleanup hitter held his right arm and hand as he jogged down the first-base line, and he seemed to be in serious pain as the inning ended. Pasquantino bent over still holding the hurt area as Matheny and a Royals trainer came out to check on him, then he went immediately into the dugout tunnel with the trainer.

¡°Just a little bit of pain in the shoulder,¡± Pasquantino said after Monday's game. ¡°That¡¯s really it. I¡¯ve felt similar things before in the past, which makes me not worried about it. We¡¯re just going to make sure it¡¯s right and get back in there as soon as possible.¡±

When asked specifically what he felt on the swing, Pasquantino described it as ¡°just a little bit of pain in the shoulder.¡±

Nick Pratto subbed in for Pasquantino at first base for the remainder of the game.

The health of the Royals¡¯ young players through the remainder of the season is of the utmost importance, especially Pasquantino. The 24-year-old is slashing .263/.350/.434 with eight home runs since his callup on June 27, quickly emerging as one of Kansas City's best young hitters.

He earned American League Player of the Week honors for Aug. 8-14 when he batted .455 with four home runs and six RBIs across six games. He¡¯s reached base safely in 27 of 31 games since July 16 -- including his walk that contributed to the Royals¡¯ four-run first inning Monday -- and is slashing .306/.371/.514 with 11 extra-base hits in that time.