Rahm obliterated the field to end at 24-under and win by six shots, and his dominance quickly turned Fox's goals from winning the event, to instead securing qualification for the Open.
"I thought I need to make a couple of birdies coming home and secure that Open spot, that was the motivation coming home, and I hit a lot of really good shots down the stretch and got the reward," Fox told Radio Sport.
Having had an excellent day with the driver and irons, Fox was initially ruing his putting, missing some opportunities as he sat at one-under at the turn. However, two lengthy putts rolled in on the back nine as he sunk three birdies to secure his spot at the Open.
The result also moved Fox into 28th spot in the European Tour's Race for Dubai, in which the top 100 players earn their card to play on the Tour the following season. Fox says that having his card secured for next season will have positive effects for his golf the rest of the season.
"It's nice having taken the pressure off, I can go out and play more how the top players in the world do - try to win every week. They're not worried about money, they're not worried about having a job, and that's a very nice position to be in."
The Open will mark Fox's second career major, having finished in a tie for 49th at the 2015 Open. He will have Kiwi company in Michael Hendry, who is also in good form after finishing in a share of sixth on the Japan Tour this weekend.
"It's been a bit painful the last couple of weeks being the lone Kiwi on tour, I copped a bit of stick from the Lions supporters so it'll be nice to have Mike up. Hopefully we can both do the country proud and play some good golf and get to play four days," said Fox.
Danny Lee missed out on qualifying, after finishing in a share of ninth at the Greenbrier Classic. Lee shot a final round one-under 69 to finish at nine-under, five shots behind victor Xander Schauffele and three shots outside of an Open berth.
He will have one final chance to book a spot at the John Deere Classic this weekend.
