I think counting Sale, ERod and Eovaldi as 1.5 SP'ers in 2021 is reasonable.
Add 1 for Perez and we're at 2.5 out of 5.
Maybe count Pivetta and Houck as 1 or 1.5 might be overly optimistic.
I'd be happy,if we added two solid and durable SP'ers, but we surely need one.