MANKATO -- Vikings rookie first-round draft pick Sharrif Floyd will have a magnetic resonance imaging exam done on his left knee today, but coach Leslie Frazier said he believes it won't be a long-term injury.

"We're not overly concerned," Frazier said Sunday morning as the Vikings returned to practice. "From what I've been told, he's just sore. So we just want to err on the side of caution. He fell on the knee. He's pretty sore this morning. The fact that he's sorer than he was yesterday makes us decide to make sure there's nothing else going on. Other than the fact it's sore, we're not overly concerned."

Overall, Frazier said the team is relatively healthy for the third week of camp. Cornerback Jacob Lacey, who was on the roster bubble as a fallback plan at the nickel slot position, will have arthroscopic knee surgery this week and will be sidelined two to four weeks. In all likelihood, the injury, which kept him from playing in Friday's preseason opener, will cost Lacey any chance of making the final roster.

Meanwhile, defensive tackle Christian Ballard (groin) is unlikely to practice this afternoon. However, those expected to return to practice include cornerbacks Xavier Rhodes (hamstring) and A.J. Jefferson (hamstring) and linebacker Desmond Bishop (groin). All three players missed Friday's preseason game.

Floyd played in the game and was active until falling awkwardly while being blocked in the first half. Floyd had a pass deflection and a tackle for loss.

In other news, Frazier said the starters will play into the second quarter in Friday's preseason game at Buffalo. Asked whether Adrian Peterson is part of that plan, Frazier said, "He's always in the conversation. We'll see where it goes with him. He's always in the conversation when we talk about our offense."