SANTA CLARA -- What rookie receiver A.J. Jenkins demonstrated in Friday's exhibition opener against the Minnesota Vikings last week was consistent with his practices.He'll make a fantastic catch. Then, he'll let another catchable ball slip through his fingers. His consistency is lacking as he faces daily mental and physical challenges.Offensive coordinator Greg Roman spoke on Wednesday about Jenkins, the 49ers' first-round draft pick."There's a lot swirling through his mind right now," Roman said. "He's trying to do everything perfectly. In that process, there's going to be a drop here, a drop there. I've seen it with a lot of players over the years where they just work through that and they start relaxing and playing as opposed to thinking and playing."A.J.'s doing a really good job all around. Would we like to see him catch every football? There's no question. I think we'll see more of that as we go. I think there's a process guys go through where there's just so much coming at them, mentally, physically, emotionally, the change of scenery, the change of the level of competition. You're trying to learn everything and when you think you got that, here comes another boatload of information, new plays, new formations, new rules. Now the soreness sets in and here comes some more plays, more formations, more this, more that."What's the solution for Jenkins?"You just have to grind through it and have mental toughness," Roman said. "Lock your jaw and just continue to push through it. Then you start to play faster. Instead of catching four out of six, now it's five out of six. You keep grinding and it's just that process. I think that's what A.J. is going through."Jenkins, of course, is a lock to make the 49ers' 53-man roster. But it's unlikely he'll get much of an opportunity to contribute as a rookie with Michael Crabtree, Randy Moss and Mario Manningham clearly ahead of him on the depth chart.