Auburn tackle Greg Robinson (left) gets in position against fellow tackle Morgan Moses of Virginia during a Scouting combine drill.

The search for a left tackle has been on the Cardinals' to-do list for a while.

It's on the to-do list for many teams.

Sometimes, it feels like finding an elite left tackle is as difficult as finding a quarterback. "That might be a little stretch," Cardinals coach Bruce Arians said, but there is little question the quest has impacted the top of the draft. Last year, three of the first four picks went to guys that are expected to be anchor left tackles for their respective franchises. This year, three more left tackles are thought to be top-10 picks among a handful that could be first round-bound.

"There is probably no other position where you have to have the size, the length, the girth but you also have to

have the feet, the athleticism, and throw into it the mentality -- that ability to forget about the last play if you gave up a sack, to handle the adversity, to have mental toughness to be able to battle for four quarters consistently," Cardinals general manager Steve Keim said. "You are on an island, you aren't always getting help and you are going against the premier athletes in the league.

"It's just hard to find. And you have to be anywhere from 6-4-and-a-half to 6-7 with a certain length on arms, with the right feet, with the right bend. There are just not that many men walking the earth with those physical traits."

The Cardinals have 6-foot-7 Bradley Sowell as the left tackle for now, but it isn't hard to speculate the team will attempt to upgrade there. Free agent-to-be Branden Albert has been the most popular name thrown around but there could be multiple quality veterans on the market – among them, Cincinnati's Anthony Collins, Baltimore's Eugene Monroe and Oakland's Jared Veldheer.

(With still a couple of weeks left in free agency, any or all of these players could end up staying with contract extensions.)

Levi Brown held down the spot for a few years but it was always a consideration to look elsewhere. Last year, with

Brown in line to start again, the Cardinals likely would have spent their No. 7 overall pick on a left tackle. Then Eric Fisher was taken first overall by the Chiefs, Luke Joekel went second to the Jaguars, and Lane Johnson fourth to the Eagles.

The Cardinals went with guard Jonathan Cooper in the first round and didn't take a tackle in the draft. Brown was traded to Pittsburgh after four games, replaced with Sowell.

This year, as many as six tackles are projected as first-round possibilities. There will not be six quarterbacks taken in the first round.

"There are not enough quarterbacks to go around," Arians said. "You can be a battler and make it as a left tackle for a season or two. Can't be a battler at quarterback."

Sowell was that battler for the Cardinals, although he struggled – a not-unexpected result for an inexperienced former undrafted rookie. Keim said as much right after Brown was traded. Drafting a left tackle high isn't a guarantee either; as rookies, Fisher and Johnson played on the right side and Joekel got hurt. None have proven themselves sure things.

"When you say how many premier left tackles are in the league, you could probably name anywhere from six to eight," Keim said. "It's similar to quarterbacks. There are a lot of other ones playing and some are playing OK. But can you reach the ultimate goal, which is winning a championship, without having a really good one? I would still probably say quarterback is the defining position but left tackle isn't far off."

The Cardinals are still trying to figure out what they want to do on the right side as well, with third-year man Bobby Massie in line to play and the possibility of veteran Eric Winston returning. But Arians has made it clear Massie can only play the right side – Winston wouldn't move either – and leaving the Cards in a spot to upgrade the left side with outside sources.

After quarterback, Keim's top priority was to make the offensive line better. That starts at tackle.

"The athleticism is usually what separates the left tackle from the right tackle," Arians said. "But now teams are catching up, putting pass rushers on the other side. Now they aren't hitting the quarterback in the back of the head, they are hitting him in the face.

"Tackles, in general, are at a premium."