Well, this is not totally true, they did try and they thought they had. Consider these things . . .
First, they have the presupposition or assumption that its easy to make a tackle a guard. That has proven to not be the case.
With this in mind, they drafted two tackles in the last draft, and for good measure, a former All-American guard.
Moreover, the coaching staff (Marrone) declared that they like the young guy back-ups, mostly free agent signings and/or practice squad raids, they had coming back from last year. The implication was, at least one of them was ready to compete for a starting job.
And, Chris Hairston, whom had been a starter at two tackle positions, was also returning.
So, if you are viewing it all through the misguided perspective of the bad assumption stated in first point, then indeed, we have the talent, its just a matter of figuring out who goes where. Right?
So, all that leads to three conclusions:
The young "talent" that was leftover from last season, really wasn't that talented.
It must not be that easy to move tackles to the guard position. Consider three pieces of evidence: 1) how bad Pears has been, 2) but neither Kojo, Hairston, or 3) anyone eles has been able to replace him.
Or. maybe it is easy, but the before mentioned players / tackles (and leftovers) just aren't that good, whether playing tackle or guard; in which case, now we have a "personnel evaluation" problem.
Or, maybe our line coaching, including the head coach whose area of expertise is line coaching, is just not very good.
My conclusion, all of the above (1, 2, 3, & 4).
Have we tried? Yes!
But, when you start with bad assumptions in your experimentations, you usually never recover from that. Or, to quote a well placed NFL coach whom we are all familiar with: "don't confuse effort with results, obviously."