Ryder Cup 2016: Will Paul Casey and Russell Knox's absence be key?

Paul Casey will not be going to the Ryder Cup after deciding not to rejoin the European Tour in 2016

Europe's bid to defend the Ryder Cup could be hit this week by the sort of Tour Championship curse that undermined the United States before their most recent defeat at Gleneagles.

Two years ago the American team travelled to Scotland in the knowledge that they would not be fielding their strongest possible line-up.

At the time, the most in-form US player was Billy Horschel. He had not been selected because the team was picked before his late surge through the PGA Tour play-offs, culminating in Tour Championship victory at East Lake.

Chris Kirk was similarly inspired, winning the Deutsche Bank Championship, finishing fourth at the season finale and second to Horschel in the play-off standings. He too was absent from the American team.

The US have ensured they don't suffer a similar fate this time by introducing what is unofficially known as the "Horschel rule".

Billy Horschel did not make the US Ryder Cup team in 2014 despite winning both the Tour Championship and the FedExCup play-offs two weeks before the Ryder Cup

It means one more wildcard decision still remains. It will not be made before the conclusion of the Tour Championship, with the recipient heading to the Ryder Cup the following week.

And come next Monday it could be Europe feeling as though they are travelling to an away Ryder Cup without their strongest line-up.

This is because Paul Casey has been the continent's most consistent recent force and Russell Knox is also in strong Stateside form. Both are playing to a standard that would make them big assets to skipper Darren Clarke's team.

But neither player is in the continental line-up even though they, along with Rory McIlroy, are the only Europeans competing in the PGA Tour finale.

Casey is ineligible for the Hazeltine match because he is not a member of the European Tour. Having played in three Ryder Cups, including Europe's 2004 and 06 victories, the Arizona-based Englishman would have brought welcome experience.

Now aged 39, he has been runner-up in the past two play-off events and was a combined 33 under par for those tournaments.

Currently fifth in the FedEx Cup, he knows victory in this week's 30-man Tour Championship would guarantee the $10m (£7.6m) play-off jackpot as well as plenty of headlines.

Casey can argue that his prominence, as the PGA Tour season reaches its climax, vindicates his decision to turn his back on the European circuit. He has followed a settled American-based schedule which has enabled him to maximise time with his family.

"Not being part of the Ryder Cup is a by-product of making that decision," Casey said.

"It was never part of that decision. I'm going to watch it with a sort of sadness that I can't be part of that."

Clarke was powerless once Casey turned his back on his native Tour. For months he has known that he will be without a player who is showing the standards that helped him to climb to number three in the world back in 2009.

With five rookies qualifying for his team, Clarke felt obliged to go for the experience of Lee Westwood and Martin Kaymer for two of his three wildcard picks. He also preferred debutant Thomas Pieters which meant Knox misses out.

Russell Knox has missed out on a place in Europe's Ryder Cup team despite being in with a chance of winning the FedEx Cup this week

The 31-year-old joined the European Tour after winning last November's WGC Champions in Shanghai because it was clear the US-based Scot stood a chance of qualifying for the Ryder Cup.

Although he ultimately did not make Europe's automatic list, he now has a realistic chance of landing the play-off title this week.

Supremely accurate off the tee, such a key attribute in Ryder Cup foursomes, Knox also possesses a sure putting touch and sits eighth on the FedEx Cup list.

Victory at East Lake, combined with play-off leader Dustin Johnson finishing outside the top three and Patrick Reed and Adam Scott worse than second, and the Inverness man would take the vast spoils on offer.

He would also pile pressure onto Clarke.

Knox's prime motivation at the moment is to prove the skipper wrong by winning the American circuit's season-long shoot-out.

Although Clarke is a canny and shrewd interviewee, his week as Ryder Cup captain would, inevitably, begin with awkward questions over his wildcard picks.

A similar scenario beset US skipper Tom Watson two years ago. The then-65-year-old had completed his team three weeks earlier and was subsequently haunted by Horschel's absence.

"As much as you want to have the hottest players on your team, sometimes it just doesn't happen that way," Watson told reporters when he arrived at Gleneagles.

"I texted him and said, 'Horschel, damn you, you're a day late but not a dollar short.'"

Yes, he deflected a negative storyline with a nice turn of phrase but the scenario became one of a number of factors that combined to undermine the veteran's captaincy.

This week might be one of those rare occasions where Clarke could be forgiven for not rooting for European success at an American showpiece event. Unless, of course, it is provided by McIlroy, who will be such an important influence in the continent's Hazeltine line-up.

Having brilliantly edged out Casey in Boston at the beginning of the month, the Northern Irishman is sixth in the FedEx Cup. Victory at East Lake would almost certainly give him the play-off title, one of the few accolades missing from a glittering golfing CV.

Were the four-time major winner to win in Atlanta, the in-form Johnson would have to finish no worse than runner-up to deny McIlroy the $10m (£7.6m) jackpot.

Such a triumph would give European golf a huge pre-Ryder Cup boost but it is much harder to make a similar case if, instead, one of its other two representatives prevails.

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