Miles Robinson couldn’t explain Thursday why his partnership with Leandro Gonzalez Pirez worked so well in the center of Atlanta United’s defense last season.

With Gonzalez Pirez since sold to Tijuana, with no reason yet provided by Atlanta United, Robinson said he’s not sure how a new partnership will work with whomever wins the the job as the other centerback. The contenders are the presumptive starter, Fernando Meza, acquired from Necaxa and Tijuana; Anton Walkes, acquired from Portsmouth; Franco Escobar or draft pick Patrick Nielsen.

Robinson thinks it will be fun, but it’s going to take time to develop chemistry and identify nuances. The team will play its first game Feb. 18 at Motagua in Honduras in the Champions League.

“I think sometimes you have to play it out to understand how players play,” Robinson said.

Robinson and Gonzalez Pirez were one of the better tandems in MLS last season. Atlanta United allowed 42 goals, second-fewest in the East and fourth-fewest overall, in the league last season. Robinson finished in the top five in Defender of the Year voting in his third season as a pro and first as a starter.

Though Robinson couldn’t explain why, the duo seemed to work well together because of Robinson’s positional awareness and Gonzalez Pirez’s aggressiveness. If Gonzalez Pirez took a chance and it didn’t work out, Robinson typically was there to snuff out the opponent’s opportunity. Former captain Michael Parkhurst once described Robinson as the best one-on-one defender he’s ever seen.

So, whichever player wins the job in a four-man backline, or the two that start in a three-man backline, they will know that Robinson is back there, ready to use his speed to run down a forward or use his height to head away passes over the top.

Atlanta United could have used his skill in its season-ending loss to Toronto in the MLS Eastern Conference finals. But Robinson was sidelined by a left hamstring injury sustained in a post-match training session in early October while he was with the U.S. men’s national team.

Atlanta United manager Frank de Boer was as aggravated as at any point during the season when discussing the injury almost two weeks later saying, “We have to have a really serious discussion with the federation that it doesn't happen again because this is a crucial stage of the whole year where we really were fighting hard to (get to the playoffs). I don't know if he can play the second or third (games) if we go through. It’s not good for him, but also not for the USA.

“He’s a USA player, and you want to perform at the highest level when there’s a lot of tension and pressure on. That’s taken away from him. So we have to have a good conversation like adults and say, ‘If we say this, you have to respect it.’ We're not saying for (no reason) that he has to take a little bit off because it’s already a very tough season for him.”

Atlanta United declined to release players for the U.S. camp underway. The reason given was the team wanted its players in its camp preparing for the Champions League.

Robinson said Thursday that he thinks he’s healthy, but hasn’t yet played 90 minutes. He also didn’t seem to object to having to work out after that U.S. game against Cuba on a cold night in Washington, D.C, saying there was no intent to injure.

“I think honestly when you are out there competing with those guys, it’s something you don’t think about,” he said. “Let me play with these national team players that I’ve been trying to play with my whole life.

“It was definitely unfortunate. Whole season you are looking forward to the playoffs. It makes me hungrier for this year.”