* Nine second round withdrawals equal record
* Llodra quits against Seppi with hamstring injury
* French compatriot Mathieu follows suit (Adds record, Mathieu withdrawal)
LONDON, June 27 (Reuters) - The second round of this year's Wimbledon has equalled the record for withdrawals and retirements for a single round at a grand slam in the professional era after two more players quit on Thursday.
Frenchmen Michael Llodra and Paul-Henri Mathieu brought to nine the number of players who failed to start or withdrew mid-match in the round of 64 while the total number of pull-outs in the tournament now stands at 12 in the first four days.
Llodra added his name to the growing casualty list when he retired during his second round match against Italy's Andreas Seppi having lost the first set 7-5.
He said later it was a hamstring problem.
Compatriot Mathieu then followed him out when retiring against Spain's Feliciano Lopez when he trailed 6-3 5-1. The reason for Mathieu's retirement was given as a neck injury.
The last time a grand slam witnessed so much medical mayhem was at the 2011 U.S. Open when nine quit the first round.
The previous Wimbledon record was eight in the first round in 2008.
On Wednesday, Australian Open champion Victoria Azarenka and men's sixth seed Jo-Wilfried Tsonga were among a record seven players to withdraw from a grand slam in a single day.
Many players blamed Wimbledon's slick green turf for the high rate of pull outs during the opening three days of the tournament but the new head groundsman said he was "100 percent happy" with the condition of the courts.
Despite failing to complete his singles match Llodra returned later to partner Nicolas Mahut in the doubles, moving through to the next round after opponents Jan Hajek and Jaroslav Levinsky retired in the first set.
"It's always difficult to make this choice," Llodra, who rejected suggestions he had let down the spectators, told a news conference.
"But, I mean, in singles it's too difficult and dangerous for my hamstrings. I prefer not to take any risks. Doubles is easier. You play halfcourt."
"I can understand it's difficult for the fans to realise or to understand my situation. But it's like this," he added. (Reporting by Pritha Sarkar and Martyn Herman, editing by Ken Ferris)