He's at 1.1 fWAR, which would be tied with flowers for 6th on braves. Mitch is K'n at 27.9% BTW, which is up 6.2% from his career year last season. Zips, steamer, and depth charts all project him in 2 range in fWAR (2.1-2.7).
Those projections are for the rest of the season...so they project him at 3-4 wins overall. Haniger is exactly the player everyone thought he was.
We do know a few things about Riley now, and none of them have to do with his 1.000+ OPS that's hyper-inflated by a .450 BABIP and 50% HR/FB rate (I'm going to assume we no longer have to discuss how unsustainable those numbers are...):
1. His power is legit, but not top of the scale. His hardest hit ball before tonight (I don't know the exit velocity on the double) didn't quite top 110 mph. That puts his raw power in the tier below Acuna/JD with Freeman/Flowers/Markakis/Albies(RHH).
2. His Z-Contact% of 60.8% is well below MLB average of ~85%. There isn't a single qualified MLB hitter that makes contact with pitches in the zone less frequently.
3. His O-Swing% is 43.3%, and would rank #3 in MLB if he were a qualified hitter, tied with Javy Baez...the poster-child for wild swingers.
4. We worry about his ability to catch up to FAs, but the league isn't throwing him many. His 46.2% FA% would rank #158 out of 170 qualified batters.
What I see so far is a good power hitter with a bit of a long swing that is guessing FA often and cheating for it. When he gets it in the zone, he causes damage. When he guesses wrong he either swings at a bad pitch, or fails to make contact altogether.
Add all that up and you get a young mistake hitter who is up there guessing, and is obviously going to K a lot as a result. Only time will tell if he can adjust to MLB quality sequencing, but MLB pitchers will let us know pretty soon. Of course, we have seen Riley make adjustments and improve many times already in many different facets of being a professional baseball player, so it would be pretty dumb to suggest he won't make adjustments at the MLB level to correct these fairly obvious issues.