NEW YORK -- T.J. Rivera's rehab from Tommy John surgery hit a snag on Friday, when the infielder experienced discomfort in his right arm during a game at Triple-A Las Vegas. The Mets planned to reevaluate Rivera on Saturday to determine if they must shut down his Minor League rehab assignment.
Recently shifted from Class A Advanced St. Lucie to Las Vegas, Rivera was in the midst of his first game at that level when he felt something in his arm.
"That's why they felt the need to take him out of the game," Mets manager Mickey Callaway said. "It was a little more than just the random soreness that you'd feel rehabbing."
A .304 hitter over two big league seasons, Rivera underwent Tommy John surgery last September. He said this offseason that he hoped for a return as soon as April, though Mets officials later began calling July a best-case scenario for him.
Making progress
If all goes well -- something that has not been the case throughout his rehab from a strained right hip flexor -- Yoenis Cespedes could return as the Mets' designated hitter in their first series after the All-Star break, July 20-22 at Yankee Stadium.
Cespedes ran at up to 90-percent intensity on Friday, according to Callaway, and could advance to a simulated game or a rehab assignment in the coming days.
"He's done enough now to warrant something a little more strenuous," Callaway said.
When Cespedes does return, Callaway added, it will be as a left fielder. Despite some internal discussion of exposing Cespedes to first base, the Mets have no plans of doing so in the immediate future.
Heart to heart
Callaway pulled aside first baseman Dominic Smith on Saturday for a brief chat about his attitude, which the manager indicated has suffered due to a lack of playing time. The Mets will decide over the All-Star break whether Smith will remain at the big league level or head back to Las Vegas to play every day.
No matter what the team's decision winds up being, Callaway wants to make sure Smith is doing as much as possible to make the most of the opportunity -- rather than stewing on a lack of chances in the big leagues.

"Quite frankly, if he feels that way when he goes down there, go down there and hit .400 and hit a bunch of bombs in a very hitter-friendly park," Callaway said, referring to Las Vegas. "That was the gist of our conversation. He definitely has some development to do, and that's why we want to get him at-bats, whether it's in the Major Leagues or in the Minor Leagues."
In the Mets' past five games, Smith has started just once. He entered Saturday batting .183 with a .529 OPS.
"I'm sure he's frustrated that things aren't going the way he wanted, and that playing time has been sparing since he's been here," Callaway said. "We just need to get him in the right frame of mind so he can go and continue to get better."