Ish Smith signed with the Pistons to be the backup point guard.

In some cases, the backup would be happy to move into the starting role.

But not Smith.

After Reggie Jackson had recurring issues with tendinitis in his left knee, coach Stan Van Gundy revealed Wednesday that Jackson will miss some time as he sorts through his treatment options.

“He’s going to be out for a while,” Van Gundy said Wednesday. “We don’t know how long — and that’ll all be determined by what he chooses to do.”

Jackson could miss as long as 6 to 8 weeks, depending on the treatment course he selects; Van Gundy said Jackson will make the decision in the next couple of days, though the options don’t include surgery.

Until then, the Pistons will lean on Smith, 28, who is in his seventh season and with his 10th team in the NBA. Smith split last season with the Pelicans (27 games, three starts) and Sixers (50 games, all starts) and posted 12.6 points, 4 rebounds and 6.5 assists.

Coming to the Pistons could be a bit of a rejuvenation, with the security of a three-year contract and more depth than he had with either team last year.

“I’ll use the experience from Philly, where I started a lot, and New Orleans,” Smith said. “We didn’t win as much as we wanted to, but I was a starter.

“Before you lead, you have to follow — whatever coach wants me to do.”

Van Gundy may need Smith to be the starter for at least the first month of the regular season, which begins Oct. 26 at Toronto. It’s a tough spot to move into, as Jackson (18.8 points, 6.2 assists) was the leading scorer and catalyst for the offense.