How much more can the Arizona Cardinals invest in the offensive line?

It is the need that keeps on going for the Arizona Cardinals.

When you ask what the biggest need for the Arizona Cardinals is heading into the 2017 offseason, the answer is offensive line.

Center, maybe.

Right guard, definitely.

Yet, I ask... Why?

How much more can the Arizona Cardinals really invest in their offensive line?

In 2013 the Arizona Cardinals picked up Paul Fanaika, they took Jonathan Cooper at seventh overall, making him the highest drafted guard in some time, but also cementing the left guard position for the foreseeable future.

They also drafted Earl Watford in the fourth round, a raw athlete who could become a cog in the wheel in a year or two and signed Eric Winston late in the season.

In 2014, they signed Jared Veldheer to a big contract, he was supposed to be the man moving forward at left tackle, he has lived up to the contract.

In 2015, they signed Mike Iupati to a massive deal and drafted D.J. Humphries in the first round.

In 2016 they signed Evan Mathis and they drafted Evan Boehm and Cole Toner.

Along the way they have signed Ted Larsen and A.Q. Shipley as potential veteran starters.

The Arizona Cardinals have invested heavy capital in four offensive lineman in five years. You can’t invest much more than that, yet, they still sit near the bottom of the NFL in offensive line rankings.

Who do you blame?

Is the the players? Were they just not that good?

Is it the coaching?

Is it the system?

How much more capital can you spend on the offensive line? Where do they invest it from? Draft capital? Free agent capital?