LONDON - Wimbledon officials warned players on Tuesday they face losing prize money if they withdraw after competing with an existing injury and are not perceived to have given maximum effort.

The All England Club will introduce the "50:50" rule at this year's Wimbledon in an attempt to prevent injury withdrawals in the opening round of the men's and women's singles events.

Several players were widely criticised last year when they played in first-round matches at Wimbledon, despite being clearly unfit, in order to claim the prize money for losing at that stage. There were a total of seven mid-match withdrawals in the 2017 tournament.

With an increased purse of £39,000 ($53,000) on offer to first-round losers this year, tournament chiefs are keen to clamp down on the issue. Players will now be able to claim 50 percent of their first-round prize money if they withdraw on site by the Thursday before the start of the main draw.

An injured player's replacement would take the other 50 percent of the prize money. But anyone who competes in the first round and "retires or performs below professional standards" could now be fined their entire prize pot. "In the wake of first-round withdrawals we pledged to act on it, and we have done so," said Wimbledon chief executive Richard Lewis.

The 2018 men's and women's singles champions will receive £2.25 million, a small increase of £50,000 on last year. Roger Federer and Garbine Muguruza won the men's and women's titles in 2017.

Lower-ranked players at Wimbledon will enjoy a greater uplift, with an increase of 10 percent across qualifying and the first to fourth rounds of the singles, boosting the overhaul prize money total to £34 million this year. The haul is larger than the Australian Open's £31 million, but slightly less than the £34.5 million available at this year's French Open. The US Open is yet to announce this year's total prize money.

Wimbledon, which starts on July 2, will reject a "shot clock" on court to monitor time taken between points. "We aren't totally convinced yet," said Lewis. "The rule is there to be enforced by the umpires. The visibility could be counter-productive. We are very content with wait and see for now."

Wimbledon bosses offered more clarity on the idea of coaching from the sidelines, which is currently banned at the tournament. "Tennis is a gladiatorial sport, you are on your own. We totally disagree with it," Lewis said.

In a bid to speed up match times, the tournament will enforce a seven-minute gap between players walking on court and the start of play.

 They are also unhappy about the amount of time being wasted by toilet breaks and on-court visits from tour physios.

"It is a concern, it's not easy to deal with. We have had discussions with people on the medical side," Lewis said. "Toilet breaks can be an issue. The word gamesmanship comes in." Keen to stay environmentally friendly, Wimbledon said no plastic straws will be used at this year's tournament as part of its sustainability ethos. Last year more than 400,000 plastic straws were used at the southwest London venue.