I like both guys a lot. I saw this as being close to a 50/50 fight when it was first on the horizon after Sterling tapped Sandhagen. Aljo is more proven in the division and has what I would argue to be the best overall arsenal of offensive wrestling and BJJ at 135, which he blends together seamlessly. On top of that his slightly unorthodox kickboxing is solid, albeit not elite.
Yan has his base in his really high-level boxing skills where few people can hope to match him, enhanced by some excellent Muay Thai. I would definitely say he outstrikes Aljo over the course of a 5-round fight, either at distance or in the clinch. Maybe not put a clinic on him or anything, but that's definutely more his world.
But the grappling is the equalizer... in theory. I think an important part of this fight is Yan's camp. He's spent time training in Dagestan with high-level wrestlers day in and day out. He's done this before and it immensely aided his game. Back in ACB, Yan's only loss was to Dagestani
Magomed Magomedov (a legit high-caliber talent recently signed by Bellator) who was able to take him down almost at will and hold him down for much of the fight. Despite this, Petr worked well off his back (seriously, the guy has a decent guard game) and showed good scrambles along with defending against submissions and GnP quite well while making good use of his time on the feet. Despite struggling with the takedowns, I scored the fight as either 47-46 Yan or a draw (depending on whether one round was a 10-8 or not), but the ref called an incidental clash of heads a "headbutt" and docked Petr a point, resulting in him getting a Split Decision loss.
Petr went to the aforementioned Dagestani wrestling camp and rematched Magomed just a few months later. Completely different story in their second bout. Yan stuffed every single shot that came his way across five rounds before punishing Magomedov relentlessly on the feet and in the clinch. Straight-up sprawl-n-brawl to a dominant UD victory. He even went on the offensive with some wrestling of his own, picking the Dagestani fighter up and slamming him on the canvas repeatedly. It was an impressive degree of improvement in only a few months' time (with a fight against a different opponent in between the first bout and the rematch, mind you).
Bearing this in mind, Yan training at this camp gives him the slightest of edges in my mind. Petr already has a comfortable striking advantage as I see it. Training day in and day out with big, strong wrestlers who are subject matter experts in the sort of way Aljo prefers to fight (as "funky" as he seems to think his brand of wrestling may be) is just solid game-planning at the end of the day. Those reps on the mats will pay dividends if/when Aljo tries to impose his will on Petr and fails to get the fight to his comfort zone.
I've got it probably ~60/40 in Yan's favor. UD or TKO in the second half of the bout via sprawl-n-brawl. Still plenty on the table for Aljo to pull something out of the hat via experience and craftiness in a scramble. That finish on Sandhagen -- a hot contender on a 7-fight win streak -- was legitimately impressive.