The good -- Saquon Barkley's recovery from a nasty ACL injury is going well!!

The bad -- the Giants' co-owner, Jon Tisch, is not sure if the star running back will be able to suit up in Week 1.

TMZ Sports spoke with Tisch out at Michael's in New York City earlier this week ... and he told us he's pleased with what he's heard about Barkley's rehab so far.

But, he added he doesn't know if the 24-year-old will be able to begin the season on the field.

You'll recall ... Barkley shredded his knee during the Giants' game against the Bears on Sept. 20, 2020, and had to have surgery to fix the issues just a few days later.

Barkley has seemed optimistic about his chances to play in NY's opener -- which is set for Sept. 12 against the Broncos -- even posting an impressive workout video last month showing off his recovery.

Still, it's clear the Giants have no plans to rush him back ... with Tisch telling us "don't know, don't know" when we asked if the tailback would be ready to go in September.