COMMERCE CITY — The Colorado Rapids' leading scorer last season, Jaime Castrillon, remains on the transfer block — even as the team began preseason training Monday.

Rapids coach Oscar Pareja said that discussions are ongoing with Castrillon and his agent about his future with the team. News reports in recent weeks out of Colombia indicated that Millonarios, a first-division club in Bogota, was interested in obtaining Castrillon on a loan, or outright, from Colorado.

But Castrillon, Pareja said, is also dealing with an injury that surfaced in a post-season medical exam with the Rapids.

"He had an injury last year, by the end," Pareja said. "It is a serious injury. At this point, he's in conversations with the league, with his agent, with the team, to see what's the next step."

Castrillon's eight goals last season led the team in his first year in Colorado. He was signed before the 2012 season after playing with Independiente Medellín in Colombia the prior season.

"It's not an easy situration for Jaime," Pareja said. "I care about the player first, with his health. But I'm going to let the club step up with doctors to see what's next."

Castrillon was at the team's training facility Monday, Pareja said, but he did not practice outdoors and was not available.

Pareja said that after team doctors diagnosed an injury, Castrillon asked for a second opinion from doctors in Colombia. MLS rules don't allow Pareja to specify the injury, he said.

If Castrillon, an attacking midfielder, returns to the team, he would join a crowded lineup. In the offseason, Colorado traded for striker Edson Buddle, drafted forward Deshorn Brown, and signed 18-year-old Dillon Serna and 22-year-old Kevin Harbottle. Each could compete with Castrillon for playing time.

"Jaime is an important player for this team," Pareja said. "Do I want him back? Yes. But there are other things that need to be discussed."

Nick Groke: 303-954-1015, ngroke@denverpost.com or twitter.com/nickgroke