MLS: FC Dallas at New York Red Bulls

New York Red Bulls midfielder Felipe Martins (8), midfielder Lloyd Sam (10) and midfielder Sacha Kljestan (16) celebrate a goal against the FC Dallas during the second half at Red Bull Arena on April 29, 2016. (Adam Hunger | USA TODAY Sports)

Lloyd Sam spent his five-year MLS career with the New York Red Bulls. His play made him a staple of the Red Bulls' midfield, and his wide smile and jovial attitude made him a locker-room favorite.

Now he's gone.

The Red Bulls traded Sam to D.C. United for an unspecified amount of allocation money on Thursday. His teammates now must play against him as a member of their Eastern Conference rival.

"It's tough for us, because we loved him," Red Bulls forward Mike Grella told reporters after Friday's training session. "I've played in Europe for six years and it happens all of the time. It's just an ugly part of the game."

The MLS transfer window is a harsh reality of the sport. The Red Bulls must move on, which means players have a new challenge.

"There are a lot of guys that I think need to step up," Red Bulls coach Jesse Marsch said after Friday's practice. "Gonzalo Veron has a great opportunity and needs to step up his game, and now show that he understands what this takes. We need everybody to step forward in a big way and be ready to get better."

Sam wasn't in the starting lineup in the Red Bulls' two previous MLS games, and homegrown forward Alex Muyl started in his place. Veron, who has been a disappointment, has a chance to earn a consistent role.

The players who could fill the void left by the trade don't have much time. Marsch told reporters after Tuesday's practice that the Red Bulls are looking to bolster their attack through the transfer window, which closes Aug. 3.

"[Sam] was a big personality around here -- a big presence in the locker room," Marsch said after Friday's practice. "In so many ways, I enjoyed getting know Lloyd and coach him. It was hard pulling the trigger because the last thing you want to do is give one of your good players to your biggest rival."

Red Bulls midfielder Sacha Kljestan was sad to see Lloyd go.

"He's a good guy that a lot of us older guys got along with well," Kljestan said Friday. "We've got to look forward now and wish Lloyd [Sam] all the best."

They have to move on, as the Red Bulls will face off against the Portland Timbers at Red Bull Arena on Sunday.

Daniel Falkenheim may be reached at DFalkenheim@njadvancemedia.com. Follow him on Twitter @Thefalkon. Find NJ.com on Facebook.