Jack Sock is currently No. 60 on the ATP rankings, but is looking to elevate his singles play at the Citi Open, where he scored a straight-set victory on Monday. (Katherine Frey/The Washington Post)

A string of text messages between acquaintances paired Wimbledon’s victorious men’s doubles team, and since that unexpected feat, Jack Sock and Vasek Pospisil have shared a tennis bromance.

“We knew each other a little bit, but never really hung out or anything,” Sock said. “Now we’re inseparable.”

“We’re like brothers,” added Pospisil, standing beside him.

Coming off another doubles title in Atlanta on Sunday, Sock and Pospisil are undefeated as a pair, but they decided against playing doubles in the Citi Open to focus on their singles play.

Sock, a Nebraska native who lives in Tampa, won his first-round match Tuesday, beating German Michael Berrer, 7-6 (7-2), 6-4. Sock will play world No. 7 Milos Raonic on Stadium Court on Wednesday. Sock said he expects Pospisil to root for Raonic, a fellow Canadian. Pospisil, the 13th seed in singles, had a first-round bye and will meet Rajeev Ram in the second round.

Winning a doubles Grand Slam in their first tournament together over the accomplished Mike and Bob Bryan was something neither player expected, and though their doubles success fostered a strong friendship, the focus remains on singles.

For Sock, the second-highest ranked American on the ATP Tour, the U.S. Open series is an opportunity for him to play in a comfortable environment in the hopes of continuing his steady climb in rankings. Though his current fame is attached to doubles, he believes his future is in singles.

“We play doubles because we have fun, and now we’re really good friends,” Sock said. “We really enjoy it, but obviously singles will be the priority for, hopefully, the next 10 years. That’s what I want my career to be based around. I’m going around and I’m trying to win singles titles now, and I’m trying to compete in the weekends of these tournaments in singles.

“If he and I can partner up and it’s the right timing in tournaments, then we’ll play and we’ll always have fun. But singles is definitely the priority.”

They played their second tournament together at the Atlanta Open and remained undefeated by capturing a title over Steve Johnson and Sam Querrey. After a few weeks apart, Sock tweeted “reunited” with a photo of him and Pospisil posing together.

Sock, 21, advanced to the singles semis in Atlanta, moving up to No. 60 in the ATP Tour rankings. Sock lost to fellow American John Isner, who went on to win the tournament. Sock said playing the U.S. Open hard court series is his favorite because it puts him in front of home crowds. He had about 15 family members in the stands in Atlanta.

The gallery at Sock’s match on Tuesday clearly favored him, cheering his points loudly. After holding serve in the first set, Sock got an early break in the second to get out to a 2-0 lead. He held serve from there to win the set and the match. Playing Raonic, the No. 2 seed in the tournament, will be a considerably tougher test.

“He’s had an awesome year and an awesome career thus far, so for me, it’ll have to be my best tennis to beat him,” Sock said. “I’m just going to go out there and hope for the best.”

Isner said “there aren’t many forehands as good as” Sock’s. The two train together in Tampa, and he praised Sock’s work ethic in those sessions. Though Isner beat Sock in Atlanta, Sock upset Isner, No. 12 on the ATP Tour, in Newport, R.I.

“He’s got a lot of talent, and I think that’s pretty obvious,” Isner said. “I think he’s going to start to put it all together pretty soon. I think he’s going to keep moving up.”

It wasn’t long ago that Sock was a star-struck 18-year-old who got to hit with Novak Djokovic during the week of the 2010 U.S. Open. Now he expects to be playing deep into tournaments. Sock and Pospisil joined Djokovic at the Wimbledon Champions’ Ball.

Sock said winning the Wimbledon men’s doubles title with Pospisil helped his confidence in singles because it exposed him to the pressure-packed situation of playing in a Grand Slam final. The team almost didn’t happen because Pospisil was worried about his health before the tournament.

“We weren’t really expecting to win Wimbledon,” Pospisil said. “That’s a tournament you dream of winning as a kid. It was a like a dream come true, and now we’re just feeling great about everything.”

Sock said they’ll play doubles together in Toronto at the Rogers Cup and in the U.S. Open. They’re now the seventh-ranked doubles team on the Tour.

“Wimbledon has helped both of us,” Sock said. “The doubles Grand Slam is very special to us. It’s definitely helped our game overall and our confidence overall playing singles every week.”