The Giants had hoped Johnny Cueto would be able to rejoin the rotation this weekend in LA.
But back tightness during a bullpen session delayed Cueto's return.
Instead, Cueto will make his 2019 debut on Tuesday at Oracle Park against the Pittsburgh Pirates.
Stay in the game with the latest updates on your beloved Bay Area and California sports teams! Sign up here for our All Access Daily newsletter.
Tuesday's start will be Cueto's first major league appearance since he underwent Tommy John surgery last year.
In two rehab starts with Triple-A Sacramento, Cueto allowed three earned runs in 10 1/3 innings and struck out nine batters.
[RELATED: Dickerson to get cortisone shot]
San Francisco Giants
Rookie Logan Webb was the scheduled starter on Tuesday, but he will be pushed back.
The Giants didn't immediately announce how the rotation will unfold upon Cueto's return.