There’s been a changing of the guard in American men’s tennis—at least temporarily.

Steve Johnson upset seventh seed Jo-Wilfried Tsonga, 6-3, 7-6 (6), in the third round of the Western & Southern Open in Cincinnati on Thursday. With the win, he’ll become the highest-ranked American on the ATP tour when the new rankings come out next week.

Johnson will dethrone John Isner, who has been the highest-ranked American man every week since July 29, 2013.

In the second round in Cincinnati on Wednesday, Isner was knocked out by fourth-seeded Milos Raonic, 7-6 (5), 7-6 (5).

“Hasn’t sunk in yet,” Johnson told reporters after the match, according to the Associated Press. “I just found out. It’s an honor, it really is. John has held that spot for a while, and I’m just glad that there are a bunch of Americans pushing toward the top.”

Isner is currently ranked 22nd; Johnson is a spot behind at No. 23. Jack Sock (No. 25) and Sam Querrey (No. 29) are the only other American men in the Top 50.

With the U.S. Open around the corner, the 26-year-old Johnson will more than likely be the top-ranked American heading in the final major of the season.

Johnson has a golden opportunity to make a serious run at this week’s Masters 1000 event. He’ll take on 34th-ranked Grigor Dimitrov, who ousted Stan Wawrinka, in the quarterfinals. And if he reaches the semis, he won’t have to face Rafael Nadal, who fell to Borna Coric in straight sets on Thursday.