Minnesota United FC is still training indoors at the National Sports Center, despite it being a 55-degree and sunny Tuesday in May.

And the continued practice on turf is starting to take a toll on the Loons.

"It's a problem for us," coach Adrian Heath said. "We need to get out on the grass as soon as possible because we're probably, in fact, we are, we're the only MLS team now who's indoors. One or two others have inclement weather, shall we say. I think Montreal have been on grass since the beginning of April, and here we are now in May. And we really need to be out on the grass."

Starting left-back Marc Burch sat out another training Tuesday with his groin injury. Heath said Burch had previous problems when he played at Seattle in 2012-13 because the defender was always indoors training on turf. Midfielder Collin Martin also trained separately after having a "little problem" the past four or five days from working on turf so much, Heath said. But the coach is hopeful to have the 22-year-old available by the end of the week. In fact, Heath said Martin might have been on the bench for the 1-0 loss to the San Jose Earthquakes this past Saturday if not for the injury.

As for why the team hasn't ventured outside yet except one time more than a week ago, it's more to do with the pitch at NSC Stadium than the weather.

"We've had a few issues with the field is the bottom line," Heath said. "It's not in the condition that we would've liked, but it's something we're working on. But we really need to work this out."

Midfielder Rasmus Schuller, who has been dealing with a hip flexor injury and been out of the past two match-day squads, worked a bit during the weekend and trained Tuesday. Heath said as long as Schuller shows no adverse reactions, the staff will step up his workload.

There was also a new but familiar face with United, as former North American Soccer League player Jeb Brovsky began training with the team. The defensive midfielder is not on trial but rather just practicing with the team as a way to regain his form after an ACL tear in his left knee this past October.

With the primary transfer window for MLS closing Monday, the time when clubs can request the transfer of players under contract in other countries, Heath said there has been some activity around moves but nothing concrete.

"Everybody's ringing around now seeing if there's anything people want or want to do. We've been fielding a few questions in the last few days, so we'll wait and see," Heath said. "But at the moment, there's nothing jumping out at us that we feel as though we'd do. But if it does, and we felt it would improve the squad and help us moving forward, we'd do something. But we don't want to do anything just for the sake of doing it."

See below for some more quotes from Heath, including a friendly jab at this weekend's color commentator for United's 12:30 p.m. Sunday match against Sporting Kansas City at TCF Bank Stadium, airing on Fox Sports 1.