The reason? The same one that has hampered McKinnie in recent years.
"Bryant is just too heavy right now. He needs to lose weight," coach John Harbaugh told reporters Thursday. "My guess is he lost quite a bit today. He's in good shape, and he has good cardiovascular fitness, and I can tell he's worked hard. But I wasn't real comfortable putting him out there today at that weight. We will figure it out in the next 24 hours, the next 48 hours, what we want to do and the best way to deal with it. He will be out there at some point."
McKinnie reported to last year's training camp on July 30, four days late, after an offseason back injury. He also had difficulty passing the Ravens' mandatory conditioning test. McKinnie then lost his starting job and didn't regain it until the playoffs, when he emerged as a key member of a productive offensive line. In part because of that, McKinnie earned a new two-year contract from Baltimore.
Harbaugh said he wasn't thrilled to keep McKinnie out of the first practice considering those prior issues.
"We're both disappointed. I'm not sure who is more disappointed - Bryant or I - because he was pretty darn disappointed," Harbaugh told reporters. "But I was feeling pretty disappointed myself. We had a long talk about it yesterday, and it wasn't that effort wasn't put in and there's an issue. But we're going to get it fixed together, and we're going to get him out there."
Cornerback Lardarius Webb, who was limited to six games last year because of surgery to repair torn knee ligaments, addressed the media at camp Thursday and said he's in good shape.
"I'm feeling good, just easing my way back in, happy to be back out with the guys - with the new guys on the defense. It's very exciting," Webb said. "Just going to keep listening to the trainers, taking it slow easing my way back into practice. Hopefully, I'll be there for the first game."
Asked whether he trusts his knee and feels he can make all the cuts and do everything to regain his previous form, Webb told reporters, "Yes, I'm trusting it. It's just easing my way back on the field. ... I think I can be Lardarius Webb again."
Harbaugh said it's reasonable to believe that Webb will be able to play in the opener against Denver, calling it the team's target. He also hopes to see Webb able to play during the preseason at some point.
On Monday, Harbaugh revealed that the outlook for inside linebacker Jameel McClain isn't quite as positive.
The team had hoped McClain would have recovered from his spinal contusion by now and that he'd be a full participant in training camp. But it has been slow to heal and Harbaugh expanded on that Thursday, calling the situation "extremely disappointing."
"I really thought he would be there," Harbaugh told reporters. "It's just when you look at the MRI and you see what's on there, there's no denying the fact that it's not safe for him at this time, so there's no way that we are going to put him out there until it clears up."