Christian McCaffrey will miss his fourth straight game Sunday for the 49ers, but a timeframe for a midseason return is emerging after he flew to Germany this week for treatment on his Achilles injury.

The three-time Pro Bowl running back is expected back by “at least early November,” according to a report by Ian Rapoport of the NFL Network.

“It was similar to a PRP treatment, and my understanding, now that he is back in the United States, it seemed like the treatment went well, and there is a chance he could run on hard ground — grass, basically — this week, which would be a step forward,” Rapoport said Sunday.

“For those worried about McCaffrey not playing at all this year, my understanding is the 49ers are not rushing him, but they do expect him back at least by early November. That is a good sign for McCaffrey.”

Jordan Mason has rushed for 324 yards and two touchdowns in the Niners’ 1-2 start in place of McCaffrey, who led the NFL with 1,459 rushing yards last season.

The AP Offensive Player of the Year also had 67 receptions for 564 yards and scored 21 total touchdowns, including 14 on the ground.

The 28-year-old McCaffrey suffered the Achilles injury early in training camp, and he was placed on injured reserve after being a late scratch for a season-opening win over the Jets.

McCaffrey is eligible to return in a Week 6 game against Seattle on Oct. 10, but the NFL Network report indicates he could be sidelined a few weeks longer than that.