Roger Federer pleaded with Grand Slams not to be panicked into reducing matches to best-of-three sets after injured players were accused of taking the money and running on Tuesday.

Federer reached the Wimbledon second round when Alexandr Dolgopolov quit when trailing 6-3, 3-0 after just 43 minutes on Centre Court complaining of an ankle injury.

Earlier, title rival Novak Djokovic booked his second round spot in just 40 minutes when Martin Klizan, suffering from a calf injury, retired at 6-3, 2-0 down.

It meant that the Centre Court crowd had seen just 83 minutes of action involving the two men who have won 10 Wimbledon titles between them.

"I feel for the crowd," said Federer. "They're there to watch good tennis."

Seven men have retired from the first round -- on Monday, Victor Troicki quit after just 20 minutes.

That brief stay was beaten on Tuesday when Serb compatriot Janko Tipsaervic quit his match after 15 minutes.

First round losers all receive £35,000 ($45,220).

There is a rule on the main ATP Tour, but not at the Slams, that an injured player can give up his place to a 'lucky loser' from qualifying while keeping the prize money.

The thinking behind the move is to preserve the integrity of a tournament and prevent fans from feeling short-changed.

But Federer does not want to see the Slams opt for the best-of-three sets format rather than the traditional best-of-five.

- 'Give up their spot' -

"I hope it doesn't happen. But I believe that more players clearly would finish their matches," said Federer who is bidding for a record eighth Wimbledon title.

"A player should not go on court if he knows he should not finish. The question is, did they truly believe they were going to finish.

"If they did, I think it's okay that they walk on court. Otherwise, I feel they should give up the spot.

"The ATP has adjusted its rule. Maybe the slams should have a look at what they could do for the players to make it just a little bit easier."

Federer believes that players who insist on competing in the first round despite obvious physical ailments should not necessarily be damned.

"For some, they just want to be out there because they feel like miracles happen: maybe the other guy retires, or maybe the other guy is carrying an injury.

"If I win, I have a day off, maybe I will feel better on Thursday. All these things play into the equation as well. Don't forget those things as well. Could be rain, come back the next day. You never know what the player's motives are."

Djokovic said he backed the ATP rule being used at the Slams but also refused to criticise opponents who fail to finish.

"If you walk out on the Centre Court, there is a responsibility. I'm sure they tried their best, but it is what it is," said the Serb.

America's John Isner said players owed it to the fans to stay and fight on court for as long as possible.

"If it's excruciating pain, okay, you can't play," said Isner who famously played an 11-hour match spread over three days to beat Nicolas Mahut at Wimbledon seven years ago.

"If something is tweaked here or there and you feel like you can give it a decent go without hurting yourself, I think they should stay out there and I think you owe it to the fans.

"I know the Wimbledon Centre Court didn't get their money's worth today. That's for sure."

Tipsarevic insisted that with $8 million won in his career, he didn't need to play for the £35,000 he earned for quitting his match when 5-0 down against Jared Donaldson.

He said he was given the all-clear by doctors to play despite suffering searing pain in his hamstring.

"Lots of players fight through Challengers to get to the main draw of a Slam. They have to pay coaches and their teams," said Tipsarevic.

"They get the chance to earn £35,000 and I don't think anyone has the right to judge them because the same guy may then go on to a Challenger and make just 300 euros."