37 rounds played.
If you keep winning, you’re going to push up pretty quickly. I did a small test on my alt hunter. Hit 2400 in 25 matches. Could have done it even quick had I not had a couple of 1-5 matches in there. I’m sure some of the top players could probably hit 3k+ in less then 25 matches played.
MMR is a little busted. It’s heavily weighted on your placement matches. If you pull some good queues right off, you could push up much higher then you might normally be able to. The opposite is true as well. If you a bunch of hard counters to start, you’re going to have to play a lot more to find your proper ‘starting’ MMR range.