Many teammates won't say a word to him for fear of becoming the target of one of his colorful outbursts.
But on a cold rainy day last week 15-year-old Scott Brown was the brave soul who returned one of Vallow's jests with a little needling of his own. When it was pointed out that no one takes a verbal shot at Vallow the 6-foot-3 two-time All-American from Bowling Green couldn't help but smile and quip "He doesn't know the fury."
As Colorado's No. 2 goalie behind most valuable player candidate Joe Cannon Vallow practices every day with a measured dose of fury. A fiery competitor at heart he can weave a tapestry of curses and drape it over the shoulders of an offending teammate.
At first glance Vallow might be one of the last Rapids players you would want teaching your kids anything. But for the past 10 weeks Vallow has been smoothing some of his rougher edges while tutoring three high school goalies at Kent Denver a Class 3A private school in Cherry Hills Village.
"He knows his stuff as a coach said Doug Price who first contacted the Rapids about paying Vallow to coach his son senior Alex Price. "He's already really capable of leading three young men that could really tune him out if they wanted to but they don't."
Good thing for them.
"I've had some opportunities to do some individual coaching in the past and I've always passed said Vallow 27 citing a lack of patience. "I've never really felt that I could deal with kids thinking that they would talk back thinking that they wouldn't listen and thinking that it would be a two-hour babysitting service as opposed to a serious workout."
Alex Price Brown and Ryan Bernstein have changed Vallow's perspective.
Each Tuesday Vallow drives to the school from the house he shares with his wife in Broomfield to run a training session straight out of Rapids practice.
Although Vallow calls the sessions personally grounding and a release the professionalism of the workout is evident from the start. Vallow stresses technique agility and footwork - qualities that made him a star in college and helped him push through the ranks of soccer's A-League where he was the goalkeeper of the year and a two-time champion.
"The one thing for me is having good footwork Vallow said. "I mean taking small steps so we can eliminate the full-out power dive. In place of that we take two or three small steps and then a shorter dive. It's a tighter dive and gives you more control."
With control comes confidence something Vallow exudes. He hammers shots at his three students evaluating their every tip catch and miss. He stresses a strong voice when balls are crossed into the penalty area teaching them that vital territorial presence.
One thing he doesn't teach is the razor tongue. Rapids goalkeeping coach Mark Dougherty noted the sharp contrast between Vallow as a player and teacher: "He's very professional shares his knowledge and is very friendly. He's an overall great guy."
His behavior with his teammates might cause some to wonder if Vallow is missing a screw or two.
"People say you have to be crazy to be a goalie in the first place which I think has some validity to it Vallow said. But his students aren't concerned.
"He's just like one of us said Bernstein who backs up Price on the varsity squad. "He can tell us what to do in a nice way so we don't get down about it. We want to work hard not because he's forcing us to but because we want to with the way he motivates us."
Brown already has decided he wants to follow in Vallow's footsteps. Price also a standout hockey player hopes his rapidly evolving skill will transfer to the college game.
One thing each of Vallow's students says he has gained is a role model and friend.
"I think a lot of times the perception of professional athletes is that they're people apart and that's not the case especially with Scott Alex Price said.
That comment brings a smile to Vallow's face.
"It's something that I've really embraced Vallow said. "I look forward to every Tuesday coming out here and dealing with these yo-yos.""