(Reuters) - Russell Knox has said watching the Ryder Cup will be a bittersweet experience after the Scot was overlooked by Europe captain Darren Clarke despite being the highest-ranked player outside of the nine automatic qualifying spots.

Ryder Cup veterans Lee Westwood and Martin Kaymer, and the in-form Thomas Pieters were selected as wildcards ahead of world number 20 Knox on Tuesday as Clarke confirmed his 12-man team to defend the trophy against the United States in Minnesota.

Clarke admitted that leaving Knox out of the three-day event starting on Sept. 30 in Hazeltine "was probably one of the toughest calls" he had to make.

"It's going to be difficult for me to watch the Ryder Cup but I probably will and I'll be rooting for the team of course. I wish them all the best and hope they win," Knox told British media.

"Of course, I feel like I deserve to be there and should be playing but I'm not, so I have to respect the decision that's been made," added the Scot, who won the WGC-HSBC Champions event in Shanghai last November.

"Every year, there's a guy in my position that doesn't get picked and it's a story right now, but in a couple of week's time when it all starts, I'm sure it'll be forgotten that I'm not in the team."

Knox, however, hoped to use the disappointment of missing out to his advantage in the FedEx Cup with the 31-year-old currently sitting seventh in the standings ahead of the last three events.

"It's certainly motivated me for the next three weeks, that's for sure. I have to use this as a springboard to try and win the FedEx Cup," he said.

"I've never wanted to prove someone wrong so badly in my life, I think. It's not sour grapes or anything. Darren had an extremely difficult decision and all of those three guys were worthy of a pick."

(Reporting by Shravanth Vijayakumar in Bengaluru; Editing by John O'Brien)