Bills coach Doug Marrone confirmed Monday that Spiller's injury is to his thigh and not his knee, insisting that "we believe he'll be fine."
Spiller said he anticipates playing against the Ravens.
"A little sore but shouldn't be anything that will keep me out this week," Spiller said Monday. "Should be feeling better day to day, but just taking it slow."
The Bills originally announced that Spiller injured his knee during Sunday's loss to the New York Jets.
Spiller, who said he did not know exactly when he was injured, was ineffective in the first half against the Jets, gaining just 9 yards on nine carries. He rushed for no gain with 14:39 remaining in the third quarter, his last touch.
"Starting in the second half, I wanted to give it a go and see how it would feel," Spiller said. "I just felt like I couldn't get any power, that explosiveness that I would [use to] cut off my leg.
"Ultimately I just came out of the game because, to me, I'm not going to put my team in jeopardy. And then also, I have to protect myself. The best thing for me to do is swallow my pride at the moment and let my other guys go in there and fight."
Expectations are high for Spiller, who the Bills said would get a heavy workload this season. Through three games, he has rushed 43 times for 153 yards and no touchdowns.
In his place Sunday, the Bills leaned on veteran Fred Jackson, who rushed seven times for 72 yards, 59 of which came on a third-and-1 play.
ESPN NFL Insider Adam Schefter contributed to this report.