Jack Sock, John Isner both upset in second round at Wimbledon

John Isner makes another early exit from Wimbledon. (Getty)

The Slam struggles of tennis’ top American men continued on Thursday with two of the nation’s four ranked players — No. 18 Jack Sock and No. 21 John Isner — both falling in the second round.

Isner, playing in the early morning stateside, fell to Dudi Sela of Israel in a disappointing effort. Isner led two sets to one but lost a tiebreak in the fourth set and then 3-6 in the fifth.

Sela, ranked 90th in the world, stands just 5-foot-9, more than a foot shorter than the 6-10 Isner. And though Isner produced 45 aces, he went just 2-of-14 on break opportunities (including 0-of-6 in the fifth set). Sela also converted two break points, but he needed just five opportunities.

“It’s all between the ears, I think,” Isner said. “I had opportunities, of course. When I don’t go for it, bad things happen. That was the case throughout the whole match, me not going for it.” Isner, 32, is still yet to advance past the third round at the All England Club.

Sock didn’t fare much better. Austrian youngster Sebastian Ofner — ranked exactly 200 spots below Sock — defeated the American 6-3, 6-4, 3-6, 2-6, 6-2. Just 21 years old, Ofner showed impressive focus after Sock came back from two sets down to force a decisive fifth. Sock converted on just three of 15 break points in the match and double-faulted four times in a fifth set that quickly got away from him.

Additionally, top American youth Francis Tiafoe lost in straight sets to Germany’s Alexander Zverev. Though Zverev, the No. 10 seed, is just nine months older than Tiafoe, he showed his superiority, needing just 93 minutes to win 6-3, 6-4, 6-3.

No. 11 seed Tomas Berdych needed four sets to send American Ryan Harrison packing as well.

Not all was lost for the United States men on Thursday, though, as 20-year old Jared Donaldson beat Italian veteran Paolo Lorenzini 6-4, 7-6 (7-0), 6-7 (0-7), 6-2. Donaldson joins 24th-ranked Sam Querrey and 26th-ranked Steve Johnson as the three American men through to the third round.