McCaffrey (back) will not practice Tuesday, Matt Barrows of The Athletic reports.

EDGE Analysis

Per David Lombardi of SFStandard.com, McCaffrey said the back stiffness isn't anything serious. McCaffrey dealt with the back issue earlier this month but was ultimately active against the Titans back in Week 15. He hasn't been listed on the injury report since, but the Niners are coming off a back-and-forth fight with the Bears on Sunday night and have a quick turnaround for the battle for the NFC's No. 1 seed against the Seahawks on Saturday night. More will be known about CMC's availability for Week 18 as the week progresses.