SANTA CLARA — A.J. Jenkins' staunchest supporters inside the 49ers locker room were stunned at Monday's trade that dealt him to the Kansas City Chiefs, who traded fellow wideout Jonathan Baldwin in return.

Jenkins apparently was having breakfast at the team's training facility when he also surprisingly learned his tenure was done, only 16 months after the 49ers made him their first-round draft pick.

"I talked to him and told him real fast: 'Make the most of your opportunity. You wanted a fresh start and you got it, so go do it,' " wide receiver Kyle Williams said.

Williams referred to Jenkins as his "little brother," someone he tried to mentor both on the field and off it before Monday's news hit Williams "like a brick wall."

"It's a little shock because, to us, that's family going out the door," Williams added. "It's not a sigh of relief over here. I hate seeing him go."

Jenkins had no receptions his rookie year and just one through two exhibitions this month. While his embattled plight heated up over the past month, the pressure mounted at the start of his rookie training camp, when coach Jim Harbaugh made a passionate case that Jenkins would become an outstanding player and prove wrong the media's "scribes, pundits and so-called experts."

Tight end Vernon Davis last week singled out Jenkins as the 49ers' most promising wideout, and Davis explained Monday he did so out of a sincere belief in Jenkins' "potential."

Davis said of the trade: "It's a great situation for A.J., because he gets to start somewhere new, start fresh. It can be a wake-up call for him. I don't know whatever it is he was doing that the coaches didn't like, or the organization didn't like. I try to stay out of that, stay in my own lane.

"But I thought he was a tremendous player."

That said, Davis suggested Jenkins "take his approach toward the game up a notch," citing off-field areas to improve such as study habits.

Fellow wideout Chad Hall's initial reaction to the trade was one of unhappiness, "because he's a friend of mine."

Hall said the Chiefs are a positive landing spot Jenkins, where he'll be reunited with quarterback Alex Smith and coached by Andy Reid, who Hall previously played for with the Philadelphia Eagles.

"I told him, 'You're in good hands and keep up fighting,' " Hall said.

For more on the 49ers, see Cam Inman's Hot Read blog at blogs.mercurynews.com/49ers. Follow him on Twitter at twitter.com/CamInman.