Neither player was active during Saturday's 37-7 win over California, the team's first of the season.
Jamabo was injured during the previous game against Washington, while Phillips has been out the past two weeks since the loss to Colorado.
Neither player appeared in more than four games this season, so they could use a redshirt and preserve a year of eligibility, but Kelly isn't looking ahead.
"Safety is our first concern, so let's make sure everybody is safe before we talk about is a guy going to play for us three years from now," the coach said.
Both players likely hoped this could be a breakout season after disappointing starts to their careers.
Jamabo was a 5-star recruit and the No. 2 running back in the 2015 class, per 247Sports, but didn't reach 500 rushing yards in any of his first three seasons on campus. He was suspended for the first two games this year and only managed 12 yards on five carries in the three games he played.
Phillips was an even bigger recruit as the No. 1 overall player in the 2017 class, per 247Sports. However, he has seen inconsistent playing time when healthy and was coming off the bench prior to the injury.
They will aim to return to full strength in time for the 2019 season and potentially take advantage of the extra opportunities.