Yan on a technical and athletic level is actually probably the best opponent to beat him - he does have impressive power (he's hurt almost every opponent he's fought) and the ability to fight in all phases (pressuring/countering/pocket/clinch), plus his wrestling and grappling are pretty high-level and he does have great cardio (no one has Merab cardio though).
The problem with Yan is stylistic, he is a "downloader" that likes to let opponents show their cards first so he can counter, then once opponents get countered they let him pressure and he can start to build set-ups and momentum. That doesn't work with Merab, if you wait to download he'll just be coming at you non-stop with all types of feints, strikes, takedowns, and you are reacting and defending. It becomes an instinctively reactive fight where you lose the initiative and it's almost impossible to gain it back.
The way to beat Merab is to push him backwards and make him the one reacting, which is easier said than done. The blueprint is probably setting a high-pace yourself to force the fight in the middle and look to land lots of body/leg strikes early, don't even worry about head-shots except as counters on knees/uppercuts. Everything should be about putting out a ton of volume and not letting Merab push you back and force you to think about what he might do next.
Yan needs to fight against type here and almost be disrespectfully aggressive, which is risky because that's where you can get clobbered with a counter or give away a cheap takedown. But he'll lose if he just tries to wait and counter early, because he'll start digging a grave of cardio that will make his output and technique progressively wilt. As that happens landing fight-changing shots decrease in probability and output decreases, so you can't win a war of attrition or land a shot that takes away Merab's cardio (i.e. liver shot) or cripple a leg with low kicks
It's going to have to be a "gambit" from Yan to win his fight - just go hard and fast early and often as much as possible, assume you won't win a decision so don't try to draw out the fight and use perfect counter-tactics. It's going to take almost suicidal self-belief in his abilities, most fighters can't fight like that (in a way where they know they are going to gas later), but perhaps a man of Yan's hard character is willing to die on his sword because that's what it's going to take in terms of mentality to beat Merab.
