Yes. It goes that fast. Jameson Taillon was a pitcher who was living on a pretty razor thin margin. He's a low ground ball pitcher who outpitched his xFIP last year by a significant margin. He strikes out less than the league average. The one thing he did last year was control batted balls and limit walks.
This year his fastball is down half a mile (give or take) his Stuff+ has dipped again, and his walk rate has jumped from really good to just "controlled". He's still giving up a lot of flyballs. It's not a winning combination.
He's on the last year of his deal. For the time being, maybe he can eat some innings on a team who needs human beings (we just celebrated 4 pretty good innings from Bryse Wilson, the bar is underground right now). But he's also on the very short list for pitchers who can take a hike when the Cubs the upgrade the position. For example, right now, I would rank him behind: Boyd, Shota, Peterson and Rea. Brown and Cabrera are iffy on what you can expect either to give, but we can probably assume one of them comes back. Then add in a trade for another SP. He's probably 7th in depth. And that doesn't count a possible Jaxon Wiggins sighting or Justin Steele giving time in the rotation which are both "possible, but neither feel like it's more than a low-likelihood of happening".
Taillon as well offers nothing in relief.
Maybe his velocity rebounds and he finds some of the variance last year. But I think it does go that fast, and I wouldn't be surprised to see Jamo outside of the organization by August 1st.