PHILADELPHIA, PA - AUGUST 29: The Phillies logo at section 108 seat 32 is shown at Citizens Bank Park on August 29, 2017 in Philadelphia, Pennsylvania. Rain cancelled the game against the Atlanta Braves and is rescheduled as a doubleheader tomorrow. (Photo by Corey Perrine/Getty Images)Getty ImagesThe Philadelphia Phillies have been searching for bullpen stability while continuing their push toward another postseason appearance. Even with the club recently returning to National League contender status, the front office has repeatedly shuffled relief options in an effort to strengthen the pitching staff overall.And now it appears that one of those experiments might have officially come to its end.Six-year MLB veteran Zach Pop has elected free agency after a brief stint with the Phillies organization this season, potentially ending a tenure that lasted just seven appearances at the major-league level.ForbesPhillies’ 3-Year Slugger Cut From Roster After Short Stint With New TeamBy Peter ChawagaPhiladelphia Phillies’ Veteran Pitcher Cuts Ties With Team After Just 7 GamesRather than accept an outright assignment to Triple-A Lehigh Valley, Pop effectively cut ties with the organization and put himself back up for grabs as a free agent.“Pop cleared waivers and was outrighted to Triple-A, and the Phillies announced that Pop elected free agency over accepting the outright assignment,” MLB Trade Rumors’ Charlie Wright reported. “Because Pop has been outrighted in the past, he has the ability to reject any future outrights in favor of becoming a free agent.”MORE FOR YOUThe report also summarized the veteran reliever's path to Philadelphia.“The 29-year-old Pop has pitched in parts of six MLB seasons with five different clubs,” Wright added. “He joined the Phillies in December. Pop struggled mightily in five outings last year, split between the (Seattle) Mariners and (New York) Mets. He was crushed for 11 earned runs over 6 2/3 frames. The righty performed much better this spring, posting a 3.86 ERA across nine appearances during exhibition play.”ForbesYankees’ Aaron Judge Solution Could Mean Cutting Giancarlo StantonBy Peter ChawagaPhiladelphia Phillies’ Former Pitcher Made Unique History In Short StintWhile Pop's stay with Philadelphia proved brief, he did manage to carve out an unusual place in team history during his short time with the organization.Pop was the first player in franchise history to challenge a pitch using Major League Baseball's newly implemented automated ball-strike review system.“When right-hander Zach Pop tapped the top of his red Phillies hat in the eighth inning on Thursday’s Opening Day, he added himself into the franchise history books,” Phillies Nation’s Ty Daubert pointed out. “Pop became the first Phillies player to challenge a pitch under the newly implemented automated ball-strike system.”Ultimately, however, Pop's tenure with the Phillies might not be remembered by many fans, even for a history-making moment. The organization acquired him hoping he could provide bullpen depth after an encouraging spring, but the partnership never developed into a long-term fit.Over parts of six major-league seasons with the Miami Marlins, Toronto Blue Jays, Mariners, Mets and Phillies, Pop has compiled a career 4.83 ERA across 170 appearances while primarily working as a middle reliever.Now back on the open market, the veteran right-hander will look for his next opportunity, though that could mean another stint with the Phillies.