He's up there and it's not just a case of short term memory calling him one of the best. He stacks up with the top guys we've had here (at least in last 15 years) in a lot of metrics. Wyatt's season is one for the record books so far as well, though we'll see how both finish the season.
I took the top sub-3.2 ERA regulars since 2002 to compare since that's as far as the online stats go to.
ERA - For guys who were majority starters, Gunner's ERA is easily tops. Next best starter ERA was Buddy Glass in 2006 with a 2.17. When you include relief guys, only D-Mo in 2016 was higher.
Opponents average, Wyatt is tops allowing a 0.126 right now. D-Mo last year, Justin Robichaux in 2008 and Gunner this year are the only other ones under .200 and Gunner is the only starter in that group.
In terms of WHIP, Wyatt is about dead on with D-Mo's number last year. D-Mo finished with an amazing 0.79 and Wyatt is at 0.78 now. Gunner is at 0.83. Taking the best seasons since 2002 (sub 3.25 ERA regulars), these are the 3 best WHIP's over that span. D-Mo didn't qualify nationally last year since he didn't average 1 IP/team game though he would've been #1 by a long shot.
In terms of K/BB ratio, Osborne's 2010 year (5.33) is tops because of his ridiculous walk numbers. Danny Farquhar's 2007 season (5.23 - mostly out of the pen) was next best. Then Wyatt this year (4.63), Gunner's 2015 (4.35) and Gunner's current year (4.31.) Gunner and Osborne are the only starters in that top 5.
Strikeouts/9, Wyatt is so far ahead of all others it's pretty amazing. He's at 15.25 K/9 IP. Next closest was Farquhar in 2007 with 11.81, then D-Mo last year with 10.69, Justin Robichaux in 2008 with 9.48 then Gunner's current season at 8.89. Gunner is the only starter in that top 5
Hunter Moody didn't stand out as tops in a lot of these categories, but he was so consistent, especially that 2006 season where he was 12-2 and SBC Pitcher of the Year. He didn't have a single wild pitch, or balk. He didn't have an amazing K/BB ratio but all across the board he had solid numbers. Osborne had similar if not slightly better numbers his 2010 year, a little better K rate, BB rate, opponents avg, ERA. Just didn't have the support at times that Moody did, only posting a 9-4 record. Right now, Gunner's numbers are tracking as good or better.
On a whole, Gunner is currently better than the career SBC ERA mark set by Jon Lieber but it's close.