American tennis player Serena Williams has advanced to the semifinals round of the US Open after outclassing Italy's Flavia Pennetta.

The tennis star was determined to win the round and at times even looked so serious it seemed she was already angry. But a Yahoo Sports report said that she wanted to take the game one step at a time.

The game was tough for both players as they both struggled to keep their momentum which at times are disturbed by unexpected errors from both sides.

Yahoo said Williams did not have an easy game against Pennetta as the latter clearly gave her something to fight for. And fight was what Williams did, taking the first set and eventually taking the last ones.

The game, which lasted a little more than an hour, was a grueling battle between two equally skilled and determined players working to earn a spot in the semifinals.

Williams considered her win as a "very special moment" not only for herself but also for her fans and even her critics. Yahoo Sports said that the tennis star has again proven to the whole world that she can always come back from that devastating exit from this year's Wimbledon tournament.

On Friday, she is set to face Ekaterina Marakova who also defeated Victoria Azarenka last Wednesday.

"It's going to be interesting for me to do the best that I can, because, you know, she has a lot of momentum going into this match as well. She doesn't care who she plays, she gives 100%. Those types of players are often difficult to play because it makes them better," Williams said of Marakova.

Williams, who is definitely eyeing for the win, said that she wants to do better in her next games and hopes to take home the championship title.

For the men's title, Novak Djokovic beat Andy Murray in a 7-6 (1), 6-7 (1), 6-2, 6-4 victory.

"I knew coming into tonight's match that it's going to be tough, that he's going to go for his shots, and the more aggressive one would win it. I'm glad I managed to stay fit in the end and pull it through," Djokovic told ABC News.

Murray, for his part, claimed that he had a hard time completing the game as he experienced pains on some parts of his body. "I got stiff in my hips and my back. ... I don't know exactly why. I didn't hurt anything. It was just, I think, fatigue," Murray said.

A year ago, Murray underwent surgery due to back cramping and his latest game proved that his stamina and physical condition could not match what Djokovic had in store for the game.