Countdown starts to players on the clock at U.S. Open

The idea of a serve clock has drawn the wrath of some of the sport's biggest names competing at Wimbledon.

World number one Rafael Nadal, who has a lengthy pre-serve routine and has often fallen foul of the slow-play rule, took a swipe at the plan saying it would affect a player's tactics and he could not support the idea.

Former world number one Novak Djokovic described the decision as “disrespectful” to the players.

Following each point, the score will be entered and announced by the chair umpire triggering the start of the clock.

If the player has not started the service motion at the completion of the 25-second countdown, the chair umpire will issue a time violation.

The warm-up period before matches will also be put on the clock.

A one-minute countdown will begin when the second player arrives at their chair and if the players are not at the net in the allotted time they will be subject to a fine.

A five-minute warm-up clock will begin after the coin toss with the chair umpire informing players of the minutes remaining at intervals of three, two and one minute plus 30 seconds.

That will be followed by another one minute countdown at which point the players must be in position and ready to play.

"These rule changes were a result of collaboration and consultation between all three organizations, and are aimed at increasing pace of play and ensuring a consistent set of enforcement standards," the USTA said in a statement.

As well as the U.S. Open, which starts in August, the following events will introduce the changes: Citi Open (Washington, D.C.), Mubadala Silicon Valley Classic, (San Jose, Calif.), Rogers Cup (Montreal and Toronto, Canada), Western and Southern Open (Cincinnati, Ohio), Connecticut Open (New Haven, Conn.), and Winston-Salem Open (Winston Salem, N.C.).

(Reporting by Steve Keating in Toronto; Editing by Ken Ferris)