ATLANTA -- Walking around SunTrust Park on Monday without a noticeable limp, Noah Syndergaard played catch and went through a series of agility drills -- his first action since straining his right hamstring Saturday against the Cardinals. Syndergaard declared himself in “tip-top” shape but did not comment further, and Mets manager Mickey Callaway brushed aside talk of how long the right-hander might be sidelined.

Later Monday, Syndergaard said he hopes only to miss one start.

“It’s really encouraging just going out there and not really having any limitations, not feeling any pain,” Syndergaard said, noting that he felt only a slight pull in his hamstring during his afternoon workout. “So we’re just taking things day-by-day.”

Even if Syndergaard returns when he’s first eligible on June 26, essentially missing one start, the Mets will need to find a substitute to start at least twice -- once this Thursday in Chicago, and once on June 25. While Callaway said the Mets have “several internal options” and will “weigh those in the next couple days,” he mentioned Wilmer Font as a prime candidate to fill in for Syndergaard.

Font pitched three shutout innings of relief Sunday against the Cardinals, throwing 55 pitches, and he is stretched out longer than any other candidate at the big league level.

“It makes him very intriguing,” Callaway said of Font, who made multiple spot starts for the Mets earlier this season. “The fact that he got to throw the amount of pitches he threw, kind of stretched out, it definitely puts his name on the radar for that.”

Other candidates to replace Syndergaard include rookie Walker Lockett, who owns a 3.28 ERA in four outings at Triple-A Syracuse, and veteran Ervin Santana, who made his first start for Syracuse on Sunday. Reliever Seth Lugo is not a candidate because the Mets value him too much out of the bullpen. Nor is seventh-ranked prospect Anthony Kay, whom the Mets do not feel is quite ready to make his big league debut.

Syndergaard is 5-4 with a 4.55 ERA in 15 starts. The Mets classified his hamstring strain as “low-grade.”

Reunion absence

Nolan Ryan, who played an important role in the Mets’ 1969 World Series championship, will not attend the team’s reunion weekend June 28-30 at Citi Field. Team officials had been expecting Ryan, a special advisor in the Astros organization, to fly to New York for the event.

Ryan did not give a reason for his absence, a source said.

Just 22 years old in 1969, Ryan appeared in 25 games that season, starting 10 of them. He saved some of his best work for the postseason, throwing seven strong innings to win National League Championship Series Game 3, then recording the final seven outs to record a save in World Series Game 3. The Mets traded him and three others in 1971 to the Angels, where his Hall of Fame career took off.

In addition to Ryan, Tom Seaver, Al Weis, Gary Gentry and coach Joe Pignatano will not attend the Citi Field reunion due to health or family reasons. Most other living players and coaches will be on hand.

From the trainer’s room

Outfielder Brandon Nimmo flew to Los Angeles this week to receive a second opinion from Dr. Robert Watkins, the neck and back specialist who spearheaded David Wright’s rehab during the final years of Wright’s career. Mets doctors previously diagnosed Nimmo with a bulging disc in his neck, publicly referring to the injury only as “inflammation.”

The pain in Nimmo’s neck recently subsided enough for him to begin a Minor League rehab assignment, but he was a late scratch from a game last week due to continued neck stiffness. As a result, Nimmo booked an appointment for a second opinion.

“We don’t quite know what’s going on, so we don’t have a timeline for anything,” Callaway said.