Comparing Triston to Civale this year is slightly disingenuous considering Stix threw a whopping 10 innings this year as opposed to Civale's 52.2, but I digress...
When Civale has been healthy, he's been above average. Keyword, when healthy, but last year his FIP was 3.87 (still above average) and this year it's 3.62. Even if he regresses a little and it ends up being a number similar to last year, it's still above average and more than just a fifth starter. Again, by no means am I saying he's an ace, but over the last two years when he's been healthy, it HAS been sustainable.
Heck, even let's look under the hood a little more on Civale...
76th percentile in MLB in Hard Hit %
66th percentile in xERA/xwOBA
72nd percentile in xSLG
88th percentile in Barrel %
93rd percentile in fastball spin
96th percentile in curveball spin
61st percentile in chase rate