By Chris Oddo

(July 31, 2013) -- 21-year-old Ryan Harrison reached his first tour-level semifinal in over a year at last week's BB&T Atlanta Open just a few weeks after falling out of the ATP's top 100 for the first time since July of 2011.

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And he did it with a completely different coaching team. Coincidence, or not? You be the judge.

Harrison, who reached a career-high ranking of 43 last summer, recently parted ways with coach Tres Davis, and has since sought the help of the USTA's Head of Men's Player Development, Jay Berger, as well as former world No. 4 Brad Gilbert.

After a quick training block in Florida, Harrison appears to be hitting the ground running in the new arrangement. He notched a decisive, straight-sets win against the always feisty Lleyton Hewitt on Tuesday at the Citi Open in Washington, D.C.

“Jay and I have always had an extremely close relationship, and been very proactive and involved in my tennis every since I met him really,” he told Romi Citkovic of Tennis Grandstand this week in Washington, D.C. “I had a really good training week down there after I lost in Newport, and played well last week ([n Atlanta]. And Brad [Gilbert] being involved is nothing but beneficial. He’s obviously got an extremely talented mind. I’ve had some advice from him and it’s been nothing but good.”

The efficacy of Harrison's new coaching arrangement will be put to a sterner test Wednesday evening at the Citi Open, as the American will take on top-seeded Juan Martin del Potro. Harrison took a set of the 2009 US Open champion at last year's US Open, but the bigger dilemma that the 21-year-old faces is that he has lost all 17 matches he's played against top 10 competition in his career.

To make matters worse for Harrison, Del Potro, with a current ranking of No. 7 in the world, has won his last 10 matches at the Citi Open. He won the event back-to-back in 2008 and 2009, and is making his first appearance in the nation's capital since.

Harrison knows that regardless of who is coaching him up, the difference between success and failure on the ATP tour is quite thin. It will be up to him—not his coach—to win the close matches, ones that he has lost quite a few of in recent months.

“You never really know what is going to happen,” Harrison told Tennis Grandstand. “I also was down 1-2 break point in the third set of the first round of Atlanta – those are just moments that could change here and there … (But) I believe that the work I put in that week-and-a-half down in Boca certainly helped out in my Atlanta run and getting a good win here today.”

(Photo Credit: Mark Peterson/ Corleve)