How Thresh became suddenly OP
Thresh wins more than any other support in League of Legends, with a combined winrate and playrate of 54 and 39 percent respectively, according to League stats website OP.gg.
Thresh is one of League's most difficult support champions. The Chain Warden's winrate and playrate have both lately spiked to be higher than any other support, placing him at the forefront of the meta—despite his high degree of difficulty. But what happened to suddenly throw Thresh into the OP category? Only one month ago, his winrate was at a mere 50 percent, and he wasn't played nearly as much.
The answer is a tricky one to understand, because nothing was changed on Thresh directly that buffed him. In fact, even the massive item changes of Patch 7.9 didn't affect his normal items, so you'd think that he would have stayed relatively the same. It wasn't him, and it wasn't items, so that leaves one more possibility—the meta.
Yep, the meta has caused Thresh to shine. With the reworking of many of League's most popular tank items and a few tanks receiving individual buffs of their own, the harass-fueled support mages and high-damage junglers have begun to fall out of favor. Utility and crowd control supports have been on the rise since then. In the utility category are Janna, Soraka, and Sona. In the crowd-control tank arena are supports like Braum and Tahm Kench. With solid tools for protection and initiation both ingrained into Thresh's kit, he's the perfect combination of both types of support champions, and so he reigns supreme at the top.
It's tricky to balance a champion that only became OP because another class of champions fell out of meta. Unfortunately for Thresh, his staggering combination of highest winrate and playrate in his role can't be ignored. Thresh's kit gives him his identity as a catcher, so don't expect any nerfs to his raw strength or shield power. Instead, changes will probably be made to make missing his hook-flay combo more punishing.
If that's the route Riot will take, we'll likely see increases in mana cost, or higher cooldowns, particularly on his Flay. The cooldown and mana costs on his hook are already rather high, but landing a good Flay can all but guarantee a hook to land afterward. If the cooldown and mana costs aren't altered on his Flay, its range may be reduced instead, forcing the Chain Warden to get closer to his opponent to land his easy combo. That would put him at much higher risk if he chooses to initiate a fight with his Flay rather than his hook, which is a common strategy.
Riot hasn't hinted that Thresh will be targeted with nerfs in the next patch, but it seems clear that something will be done about him soon. Champions rarely go very long with stats this high without Riot stepping in and swinging the nerf hammer.