The 2012 U.S. Open continued Monday, and two of the most notable names advanced to the fifth round.
On the men's side, No. 1 seed Roger Federer moved on when his opponent, No. 23 seed Mardy Fish, withdrew from the tournament for health reasons.
"I regret that I have to withdraw from the U.S. Open for precautionary measures," Fish said in a statement.
Tomas Berdych, the No. 6 seed, also advanced with a 7-6, 6-4, 6-1 win againt No. 11 Nicolas Almagro.
No. 4 Serena Williams continued her strong play, advancing to the fifth round with a 6-0, 6-0 win against Andrea Hlavackova. Williams is yet to drop a set in four U.S. Open matches. While Williams advanced, No. 6 seed Angelique Kerber and No. 2 seed Agnieszka Radwanska both lost in straight sets.