FRISCO, Texas -- Offensive line coach Frank Pollack will not be back with the Dallas Cowboys in 2018, as he joined the Cincinnati Bengals on Thursday.

It is the sixth change on Jason Garrett's staff since the season ended and perhaps the most significant, because of the resources the Cowboys have put in their offensive line and their desire to be a run-first team.

Paul Alexander, who spent more than 20 years with the Cincinnati Bengals, is interviewing with the Cowboys as Pollack's replacement, according to a source. A source said Tom Cable, who was fired by the Seattle Seahawks and was a college teammate of offensive coordinator Scott Linehan, is also a candidate.

Frank Pollack will not be back as the Cowboys look for a new assistant coach to run their offensive line Tim Heitman/USA TODAY Sports

Assistant offensive line coach Marc Colombo, who played for the Cowboys from 2005-10, will also be in the mix.

Pollack took over for Bill Callahan after the 2014 season. Dallas was in the top 10 in rushing -- including second in both 2016 and 2017 -- in each of Pollack's three seasons as the line coach.

During Pollack's tenure, left tackle Tyron Smith, center Travis Frederick and right guard Zack Martin made the Pro Bowl each season and all three were first-team All-Pro picks in 2016. Pollack also oversaw the move of La'el Collins from left guard to right tackle in 2017.

Pass protection, however, was an issue in 2017. Dak Prescott was sacked 32 times after he was sacked 25 times as a rookie. The Cowboys missed Smith for three full games and all but three snaps of a fourth. In the first game Smith missed, Prescott was sacked eight times by the Atlanta Falcons, with backup tackles Chaz Green and Byron Bell giving up six sacks. Without Smith on the field, Prescott threw one touchdown pass. The protection was better with Smith on the field, but Prescott's yard per attempt dropped from 8 to 6.8 in 2017.

Pollack joined the Cowboys in 2013 as Callahan's assistant offensive line coach. When Callahan left for the Washington Redskins, Garrett promoted Pollack, who is a stickler for details and technique.

Pollack joins special-teams coordinator Rich Bisaccia, wide receivers coach Derek Dooley, quarterbacks coach Wade Wilson, secondary coach Joe Baker and tight ends coach Steve Loney as coaches not returning. Bisaccia was named the special-teams coach with the Oakland Raiders, and Dooley became the offensive coordinator at Missouri. Loney is retiring, and Wilson and Baker had expiring contracts.

Running backs coach Gary Brown, whose contract ran out, also reportedly interviewed with the Raiders and has drawn interest from at least one more team. The Cowboys, however, want to keep Brown. Passing game coordinator/linebackers coach Matt Eberflus and secondary coach Greg Jackson also have expiring contracts.