Pat Clark Motorsports' Ben Bostrom will be replaced by Jake Holden in the final round of the AMA Pro Road Racing series after he was forced to withdraw with nagging injuries suffered in the previous race at New Jersey Motorsports Park.Bostrom broke ribs in a strange, inexplicable high-side early in Sunday's race at NJMP. The bike snapped sideways while Bostrom was on a short chute between turns one and two, sending Bostrom and his Yamaha YFZ-R1 into the air. Bostrom was quickly on his feet and looking for the Yamaha, which he saw "lawn darting" into the tarmac.A post-race examination of the data failed to reveal a cause for the motorcycle to react so violently. The worst injuries were broken ribs, which have been reluctant to heal."Basically, Ben's still injured from the crash he had in New Jersey," team manager Ron Heben said. "We were kinda hoping it would heal up and he'd be able to ride. You never know how long a rib's going to take to heal up."Heben said the team was disappointed that Bostrom wouldn't be able to finish the season. Bostrom was fast at the June Barber test and was looking forward to the race."With everything that's going on, Ben had a chance win both races," Heben said. "Now that's not going to happen."Bostrom didn't have a stellar start to the season, but turned it around beginning at Infineon Raceway, where he carded a pair of seconds. The next four races only yielded one podium before he broke through with his first Superbike win in six years at Mazda Raceway Laguna Seca. That was followed up by a pair of seconds at Virginia International Raceway and a third in the first race in New Jersey. Then came the crash.Bostrom currently sits fourth in points, but is likely to lose the spot to Larry Pegram."In an effort to put another bike on the Superbike grid, Jake Holden is going to ride," Heben said.Holden has been the ultimate pinch-hitter this year. He started the season without a solid ride-he rode his own Honda at Auto Club Speedway-before standing in for John Hopkins on the M4 Monster Energy Suzuki. Holden took over the Suzuki at Infineon Raceway after Hopkins had much-needed wrist surgery.Holden had gradually improving results from Infineon Raceway to Laguna Seca, where he finished fourth in the American SuperBike race. When Hopkins returned at VIR, Holden was again out of a Superbike ride.But by then he was well into the Vance & Hines XR1200 championship. The Oregonian raced an RMR Bruce Rossmeyer Daytona Racing XR1200 to second place in the first race, then third in the next two. When triple race winner Danny Eslick decided to sit out the New Jersey Motorsports Park round, Holden stepped in to take the win. But a post-race teardown found a discrepancy with the ECU and Holden was later stripped of the win.Eslick and Holden are among the 11 riders entered for the final XR1200 round this weekend at Barber.