It'll come back. I've hit it with a ton of Tenacity. It seems dead but new sprouts come out when the Tenacity applications end. Even on a blank canvas of a new seeding, triv has no problem sprouting--maybe less but who really knows.

I had wanted to try Velocity but seems it is no longer made and the ag equivalents are super expensive.

I still try to hit it with Tenacity very early spring and avoid irrigation in the summer to let the lawn go dormant. Has kept it in check.

That's what I'd like to do is keep it in check and try and get the other grass thicker around it. Do you think spraying it summer is a bad idea? I mean it's still growing.

Go ahead and spray it in summer if you like. I've had the opposite experience with both annua and triv. Spray a few times, down it goes, and I don't see it again unless it reseeds. And it seems to be less of a problem every year.

I just knocked out one triv patch and that, so far, is that. I don't expect to see it again and, so far, haven't.