Rory McIlroy says his relationships with several former Ryder Cup team-mates have strained by their decisions to join the LIV Golf series.

Five members of Europe's team for the 2021 tournament, at which they were well beaten by the United States at Whistling Straits, have joined the controversial Saudi Arabia-backed circuit.

Four of those five – Ian Poulter, Lee Westwood, Sergio Garcia and Bernd Wiesberger – are part of the field for this week's BMW PGA Championship at Wentworth.

The presence of LIV golfers at the DP World Tour's flagship event has been criticised by some players, with former world number one Jon Rahm and defending BMW PGA champion Billy Horschel both hitting out at their participation. 

McIlroy has been a fierce defender of the PGA Tour amid the divide with LIV Golf, and admits he has grown distant with many of his counterparts on the breakaway circuit. 

"I wouldn't say I've got much of a relationship with them at the minute," McIlroy said of his former Ryder Cup team-mates.

"But, like, I haven't done anything different. They are the ones that have made that decision. I can sit here and keep my head held high and say I haven't done anything differently."

Having declared last month that it would be "hard to stomach" LIV players joining the field at Wentworth, McIlroy was more diplomatic this time around, adding: "They are here. They are playing the golf tournament. 

"My opinion is they shouldn't be here, but again that's just my opinion.

"But we are all going to tee it up on the first tee tomorrow and we are all going to go play 72 holes, which is a novelty for them at this point, and then we'll go from there.

"If you're just talking about Ryder Cup, that's not the future of the Ryder Cup team. They've played in probably a combined 25, 30 Ryder Cups, whatever it is.

"The Hojgaards [brothers Rasmus and Nicolai], Bobby Mac [Robert MacIntyre], whoever else is coming up, they are the future of the Ryder Cup team. That's what we should be thinking about and talking about."

Meanwhile, the DP World Tour's chief executive Keith Pelley has hit out at comments from Westwood and Garcia after the two men claimed the DP World Tour is nothing more than a feeder circuit for the PGA.

Garcia, Europe's record points scorer in the Ryder Cup, recently declared the DP World Tour to be just the fifth best circuit in world golf.

"It's unbelievable," Pelley said. "Let's look at the facts. If the metric determining the top tours in the world is just money, then the number one tour is the PGA Tour, always has been. You could argue that the LIV Invitational Series is number two.

"But The Asian Tour, $22.5m; Korn Ferry Tour; $20m; Japan, $28m; Australia, $5.8m; Sunshine Tour, $7.4m. Totalling all their prize funds together comes to just half of our tour. So even if the only metric is money, how possibly could we ever become number five?

"Is this week a tournament that is on a feeder tour? A tournament that has sold-out crowds, television coverage around the world in 150 countries, five of the top 15 players in the world? A tournament with 150 accredited media?

"Our first co-sanctioned event with the PGA Tour in Scotland, where 14 of the top 15 players played, would that appear on a feeder tour? I could go on and on."

Pelley also defended his decision to remain aligned with the PGA Tour, adding: "LIV Golf and the PGA Tour are involved in a power struggle for our sport.

"It is corporate America versus a sovereign state and a conflict fought out with eye-watering sums of money. I often get the question, why can't we work with both the PGA Tour and the Saudis. We tried.

"But the Saudis remain determined to set up a new series outside of the current ecosystem. That decision has created the conflict we see today, and we chose to partner with the leading tour in the game.

"Some people might not agree with that decision. But it's a decision we feel is the right thing to do for all our members."

The 12 singles pairings for the final round of the Ryder Cup have been announced, with the United States looking to dethrone Europe on Sunday.

Team USA hold a commanding 11-5 lead following Saturday's foursomes and four-ball at Whistling Straits, where the hosts boast the biggest two-day advantage since 1975.

Steve Stricker's USA require just 3.5 points to reclaim the cup from Europe, who will need to produce the biggest ever comeback if they are to claim the required nine points to defend their crown.

"That was an important one," Stricker said after USA split the four afternoon matches. "If they blank us, they're right back in the game. I think getting two points and splitting the session is a good outcome for us."

Xander Schauffele will lead the Americans out to start Sunday's play in Wisconsin, facing struggling European star Rory McIlroy.

McIlroy was dropped for Saturday's foursomes having struggled on Friday – the first time in the four-time major champion's Ryder Cup career that he has missed a session. He returned for the four-ball but fell to another defeat alongside Ian Poulter against Dustin Johnson and Collin Morikawa 4 and 3.

The second matchup pits USA's Patrick Cantlay against Shane Lowry, while Europe captain Padraig Harrington put world number one Jon Rahm down to face Scottie Scheffler.

Bryson DeChambeau and European star Sergio Garcia meet in match four, American Collin Morikawa tackles Viktor Hovland and unbeaten USA veteran Johnson plays Paul Casey.

Elsewhere, Brooks Koepka is set to tee off against Bernd Wiesberger, Poulter and Tony Finau go head-to-head, Justin Thomas will clash with Tyrrell Hatton, Lee Westwood goes up against Harris English, Jordan Spieth faces Tommy Fleetwood and the final matchup is a showdown between Daniel Berger and Matt Fitzpatrick.