I disagree. It depends on how much time you are willing to put into training/conditioning. The guy is a strong 4.5 (maybe close to 5.0) at 26 years old. If he can spend 3-4 hours per day training (difficult given the usual life constraints, but certainly possible) he could be a strong 5.5 within 1-2 years. At that level an ATP point is not out of the question.
Again, I agree that it is unlikely, but not impossible.
Looking at his record he does not look like a strong 4.5 close to 5.0. He looks like middle of the road 4.5. The main thing I think he has working against him is he does not have a strong tennis background. He was not a strong junior and did not play college tennis and pretty much started tennis again after a long layoff. At this point he would not just need time but also a lot of money from coaching because he likely has some technical flaws. As you get higher up the NTRP ladder it gets harder not easier to move up levels. If he were a former D1 player that took off 5 years and started playing again at age 26, I would give him a chance, but basically 4.5 rec level player trying to do it is a whole different animal.