James Blake's reward for upsetting defending champion David Nalbandian 6-2, 6-4 Tuesday at the Legg Mason Tennis Classic will be a third-round matchup against his big-serving pal and doubles partner, John Isner.

Blake and Isner only have faced each other once before on the ATP tour, two weeks ago at Atlanta, and Isner pounded 30 aces en route to a three-set victory. There's little subtlety to the 6-foot-9 Isner's game — and Blake knows it quite well.

They live near each other in Tampa, Fla., and hit together all the time. They'll also team up in doubles on Wednesday, before heading to opposite sides of the net in singles on Thursday.

"We're practically neighbors. Last time I was home, I was eating breakfast at his house just about every morning. And he's taken so much food out of my fridge, I think he owes me a few thousand dollars," Blake said. "We practice together so often that I've seen his serve a million times — and it doesn't get any easier."

So what do you do?

"Sometimes," Blake explained, "you've got to just guess."

The 11th-seeded Isner, who hit a record 112 aces while winning the longest match in tennis history at Wimbledon last year, needed only six aces to get past Tobias Kamke of Germany 6-1, 6-3 Tuesday night.

Once ranked as high as No. 4, Blake won Washington's hard-court U.S. Open tuneup in 2002 and was the runner-up in 2005. But beset by a series of injuries, most recently a bad right knee, he dropped to 173rd in the rankings in March and began this week at 90th.

"If I'm 170 in the world, I'm having fun. If I'm 4 in the world, I'm having fun. Even when I retire, I'll be having fun," the 31-year-old Blake said.

His victory over the eighth-seeded Nalbandian, who had a first-round bye, allowed Blake to get to the third round for only the second time in 10 tournaments this season.

"He's definitely found his form again," Isner said, noting that playing against Blake will be "very awkward."

Blake dominated Nalbandian for most of their match, saving all three break points he faced and winning 31 of 39 points on his first serve.

"This is the best I've served in two years, probably," Blake said.

Earlier Tuesday, two young Americans — Ryan Harrison and Ryan Sweeting — won first-round matches, earning far tougher tasks in the second round.

The 19-year-old Harrison extended his strong showing on the U.S. summer hard-court circuit by overcoming 10 double-faults to beat Mischa Zverev of Germany 6-4, 1-6, 6-1. Sweeting, who turned 24 a little more than two weeks ago, defeated Alex Bogomolov Jr. 6-2, 6-4 in an all-American matchup.

Now Harrison will face No. 3-seeded Viktor Troicki of Serbia, while Sweeting takes on top-seeded Gael Monfils of France.

"I've never played him before, but obviously I've seen a lot of his matches, and I know what he's about. He's one of the most talented guys on the tour; definitely the fastest person I've ever seen — in most sports," Sweeting said.

"I'm going to have to try and finish points at the net," Sweeting explained, "because if I just stay back, then he's just going to run for days and make me look like an idiot."

In other matches Tuesday, Tommy Haas beat late fill-in Amer Delic 6-2, 6-3, Jarkko Nieminen earned his 300th career ATP match win by topping Igor Kunitsyn 7-5, 6-4, Flavio Cipolla defeated Marsel Ilhan 7-5, 6-0, Michael Berrer eliminated Paolo Lorenzi 7-5, 6-1, Kevin Anderson beat Chris Guccione 3-6, 6-2, 7-6 (0), Grigor Dimitrov defeated Tim Smyczek 4-6, 7-6 (3), 7-6 (3), and Somdev Devvarman eliminated Denis Gremelmayr 6-2, 6-3.

Delic lost in qualifying but got a spot in the main draw when 2007 Australian Open runner-up Fernando Gonzalez withdrew from the tournament, citing a bad knee, a couple of hours before he was to play Haas.

"There was a little bit of an adjustment," said Haas, once ranked as high as No. 2 but now 576th as he works his way back from right hip surgery.

"I don't really know still exactly where I'm at with my game," said Haas, who spoke about trying to decide whether he wants to extend his career for another six months or two years.

Sweeting is ranked 66th this week, one spot below his career high, which he reached in May, a month after winning his first ATP title at Houston on clay.

Harrison, meanwhile, reached the semifinals at his past two tournaments, in Atlanta and Los Angeles, to lift his ranking to a career-best 82nd.

He began playing tennis at 2, and was able to hit the ball over the net by the age of 3 — and, Harrison said, his family has the home video to prove it.

Harrison is supremely confident, on the court and off. When he was asked Tuesday where he envisions himself in two or three years, Harrison paused every so briefly before answering: "Grand Slam champion. Multiple Grand Slam champion."

No American man has won a major title since Andy Roddick at the 2003 U.S. Open, a 31-tournament drought that's the country's longest.

"We hear what people say about Americans, and us being lazy," Harrison said, then added that the current crop of up-and-comers such as himself and Sweeting are "proving that's not true."