The 27-year-old was quick to dismiss any notion that he has aggravated his oblique, and instead said the soreness stemmed from playing on the AstroTurf at Rogers Centre following a prolonged absence from the field.
"Just a little sore and trying to watch myself a little bit," said Rasmus, who was originally listed in the lineup but became a late scratch prior to game time. "I hadn't played in a month, woke up this morning a little sore and I thought it would be best not to push myself too much and be smart about it."
Rasmus didn't have the luxury of appearing in rehab games prior to his return, and the drastic increase of intensity over a short period of time could have played a role in his body not responding well.
The former first-round Draft pick of the Cardinals wasn't sure how much time he would need to rest, but with an off-day coming on Monday, it's possible Rasmus could return on Tuesday night against the Yankees.
Despite the recent injuries, Rasmus has enjoyed a breakout season at the plate. He is hitting .275 with 20 homers and 63 RBIs while posting an .828 OPS in 114 games.
"I'm not 22 anymore ... knowing that I'm just trying to make sure I keep myself healthy and I'm able to finish strong," Rasmus said. "Obviously I want to play today, but woke up a little sore this morning so I just kind of pulled the reins back to make sure I'm able to do that."
Gregor Chisholm is a reporter for MLB.com. Read his blog, North of the Border, and follow him on Twitter @gregorMLB. This story was not subject to the approval of Major League Baseball or its clubs.