Diamond 1 with mmr of challenger? can this be?

It's actually not that uncommon for challenger mmr players to end up with somewhat lower ranks due to decay, as ranked decay leaves your mmr intact. Some pro players have ended up 'stuck' with accounts that have challenger mmr befitting their skill, but might have decayed to plat or even all the way gold 1 if they found themselves unable to play on that account for an extended period (e.g. bootcamping in korea). Then since they still have challenger mmr's, they end up with 15 minute+ queue times, and it becomes a pain to climb again even with the crazy LP gains they'd have.

edit: That having been said, I wouldn't necessarily trust third party estimates of mmr. it's also possible that they do have 'only' a diamond 1 ish mmr in reality, and the sites estimations of mmr get a little janky at the extremes.

He was probably challenger at one point, maybe lost a few games. But damn, wish I could be in his place.

op.gg isn't an accurate display of MMR, that's how. They just go off their own algorithms to try and give an estimate of what each play is.

Plus this guy has 90 wins vs 40 loses...is at a 68% winrate in DIa 1. So he's not doing too bad.