Meaningless.
Willie Mays first 26 MLB At-Bats, 1 for 26, 1 HR, 1 RBI
Mike Schmidt hit .206 in a cup of coffee with the Phils in 1972 and followed that up with a .196 his first full year.
Pedroia didn’t light the world on fire his first couple months
On the flip side, Ted Cox went 6 for his first 8, 7 for his first 12 and finished his September call up hitting .368 in 1977. He lasted 4 full seasons and 272 games in the majors.
The first month or two or even year is hardly predictive.