Every starter has to be 99, including mlb2, dt2, cb2-3.
https://www.mut.gg/lineup-builder/f2a4a054-5340-4dca-892b-1bb045a2fe21/
The first I was able to make a 99 team was Feb. 26, when they updated the strat cards. Because there are no 99 K/P, you need to use The Leg strat card to make a 99 team.