But Cassar painted a different picture of the 37-year-old, seven-time MLS All-Star who holds Colorado's franchise records in most games played, games started, minutes played and who served as the club's captain from 2004 until he was traded to the L.A. Galaxy in 2013.
"When I watch Colorado play, they play with the same passion that he had and the same drive," said Cassar, RSL's first-year coach. "They never quit, and that's Pablo to a tee."
Under Mastroeni, the Rapids are off to a 4-3-3 start and are currently in fifth place in the Western Conference with 15 points, five points behind second-place RSL. It's been a positive start for the former Colorado star, who wasn't named head coach until March 8, seven days before the Rapids kicked off their 2014 campaign against the New York Red Bulls on the road.
Defender Chris Wingert played in Colorado in 2006 and 2007 and said Mastroeni's leadership ability and tenacity rank high among guys he's been around in his 12-year MLS career.
"He's maybe one of the greatest leaders I've been around in soccer, for sure," he said. "He really knows how to just get his guys up for the match. Unbelievable motivator and a great mind for the game. It's no surprise he was so successful at the international level, so when [the Rapids] named him coach, I was happy for him."
Colorado native Nat Borchers played with Mastroeni for two seasons playing for the Rapids. The RSL center back said Mastroeni's intensity and will to win makes him a player's coach.
"I think he's already made that club better just by stepping into that position," Borchers said.
As for similarities between two old pals Cassar and Mastroeni, both first-year MLS coaches?
"These guys, they bleed for their clubs. You don't always get that from head coaches," Borchers said. "Some guys are a little more at arm's-length, but these guys, I think if there's one thing they share in common, it's that they bleed for their club. They're so involved and they care."
Colorado Rapids at RSL
O At Rio Tinto Stadium, Sandy
Kickoff • Saturday, 7:30 p.m.
TV • CW30
Radio • 700 AM
Records • RSL 5-0-5, Colorado 4-3-3
Last meeting • RSL, 2 Colorado 2 (Aug. 4, 2013)