Donald Young reacts after beating Kevin Anderson Friday in the quarterfinals of the Citi Open. (Nick Wass/Associated Press)

At an ATP Challenger event in Sarasota, Fla., earlier this season, former world junior No. 1 Donald Young succumbed. The struggle to regain the form he showed at the end of 2011, when he broke into the ATP top 40, overwhelmed him.

In the second set of a first-round match, Young whacked a backhand into the net.

“Son of a biscuit!” he cried. “Biscuit, biscuit, biscuit!”

The tirade earned a warning from the chair umpire, but it also earned Young something else: more than 100,000 YouTube views and notoriety for something other than the third-longest losing streak in the Open era, the 150-spot drop in rankings that followed and the label of another once-promising young American tennis player who just didn’t pan out.

Young berated the pastry again Friday as he trailed in his Citi Open quarterfinal match against No. 21 Kevin Anderson at William H.G. FitzGerald Tennis Center. Then he rallied to win the second-set tiebreak and rolled in the third set for a 3-6, 7-6 (7-3), 6-2 victory. When it came time for match point, Young left biscuits out of it, opting instead for a few seconds of fist pumps to celebrate his first ATP World Tour semifinal since September 2011.

When Young became the youngest year-end world junior No. 1 at 16 years 5 months in 2005 or No. 38 in the world at 22, he had a tendency to sink within himself when matches began to slip. Even so, he reached the fourth round of the 2011 U.S. Open, closing that season at 39th in the world.

Then he lost a February 2012 match to John Isner. He wouldn’t win again until August, a 17-match streak of futility that merited a full-blown Sports Illustrated story, among others. Some of those stories said pressure applied early and often by his parents, who coached their only child at their academy in Atlanta, created a mental sinkhole from which he couldn’t seem to climb out.

At some point during the seemingly endless losing, Young realized his negativity wasn’t working.

“Losing’s not good, and I was doing a lot of that,” Young said. “I didn’t want to do that anymore, so I wanted to try something else.”

So he committed to being positive. He admits he still has lapses, but being down a set — as he was against Anderson — rarely begets a return to crippling negativity.

Young spent much of 2013 in ATP Challenger and 250-series events, then played his way through U.S. Open qualifying and into the round of 64 for his best Grand Slam finish since 2011. In March of this year, he brought in U.S. Tennis Association coach Craig Boynton to aid his mother and provide “a different set of eyes, a different perspective,” as he put it.

“It’s all there; he just had to find it,” Boynton said of Young, now 25. “He’s finding it.”

Young made it to the round of 32 at both the Australian and French Opens this year, and even after a disappointing opening-round exit last week in Atlanta, he said he felt his Citi Open breakthrough coming.

“I think [positive] is the only way. I’ve tried being negative. It doesn’t work. I’ve had a lot of low times,” Young said. “. . . If you look at the top players in the world, that’s what they do. They stay fighting, focused the whole time. Even if they lose, you know they’re not going away.”