Fans get a close-up view of their favorite tennis stars on the U.S. Open's first day

Practice makes perfect -- and for many tennis fans, watching stars like Serena Williams and Roger Federer practice at the U.S. Open Monday made for a perfect opening day.

Spectators flocked by the hundreds to get an up-close view of their favorite players during practice sessions -- a first for fans after construction of the new 1,300-seat capacity bleachers overlooking the practice courts.

Sherie Wilson, 49, of Atlanta, was in town for her fifth Open. She made her way from the front gate straight to the practice courts to check out the new view.

"We had to stand up on one of the other courts' seats and look through a little corner down onto the practice courts," Wilson said of the old stands' obstructed scene. "It wasn't easy. This is much improved."

The newly constructed spectator area is part of the first implemented phase of a five-year, $550 million transformation plan for the grounds at the United States Tennis Association's Billie Jean King National Tennis Center in Flushing, Queens.

The rest of the plans are on display at an exhibit called the U.S. Open of Tomorrow. The upgrades are set to be finished by 2018 and include two new stadiums to replace Louis Armstrong Stadium and Grandstand stadium and a retractable roof over Arthur Ashe Stadium, USTA officials said.

Fans hovered over each other to take photos of 17-time Grand Slam winner Serena Williams return serves during a midmorning session. Later, nearly every inch of the stands was filled with viewers for Federer's practice.

A no-standing rule in the bleachers didn't stop fans from getting a close look at the action. Many retreated to the ground-level shade to stand just a few feet from the world-renowned players. A chain-link fence and netting kept fans back but Alvaro Mantilla, 42, of Ecuador, fit his iPhone camera lens between the loops to get a shot of Federer.

"Two years ago, we could never get this close during practice. We couldn't even see them," Mantilla said of the 2012 Open. "We are enjoying this very much. He is our favorite. He is the best!"

When Federer finished with his practice time, fans clapped and cheered while one yelled, "Win the tournament, baby!"

The players, some casually dressed in T-shirts and shorts, exited a gate where fans waited with oversized tennis balls hoping for autographs. For Jack Cotten, 67, of Wilmington, North Carolina, seeing the players in this element was just as exciting as watching matches that count toward the coveted trophy.

"This is a very up-close and personal experience," said Cotten, who has been to the tournament about a dozen times. "This just makes it better. It's far more intimate."

During lunch, longtime tennis aficionados were greeted with a food concept new to the grounds: a food truck.

The country's food-truck craze finally hit the Open this year. A grilled-cheese truck served up $13 gourmet versions, like the "delicate cheese" with truffle cheese, truffle butter and caramelized shallots or a sandwich with Gouda, bacon and herb butter.

Barbara Shea, 59, of San Diego, lined up for a classic with New York cheddar and New Hampshire Landaff for $10.

"I was just walking by and saw it and knew I had to have one," said Shea. "You never see grilled cheese at tennis tournaments. This is great."