Christian McCaffrey was disappointed to suffer defeat on his San Francisco 49ers debut after a "weird week", but wants to focus on what he can control.

McCaffrey only joined the 49ers at the end of last week in a trade from the Carolina Panthers, and was thrown straight into the action against the Kansas City Chiefs on Sunday.

The Chiefs ran out 44-23 winners at Levi's Stadium, with McCaffrey only involved in 21 snaps, making 38 yards from eight carries.

The 26-year-old All-Pro was clearly still getting used to the idea of swapping Carolina for San Francisco, but said after the game he wants to get up to speed quickly.

"This was a weird week for me and for [the team]," he told reporters. "I didn't know what to expect. I know I had a certain list of plays that were up.

"For me, mentally, this was just 'focus on everything I can control and get rolling'. Obviously losing's frustrating, but I'm still getting to know these guys, I gotta do my job, I gotta make a few more plays here and just learn the offense as quick as possible.

"I'm just trying to control what I can control right now and get going."

The Niners are 3-4, having lost their last two games, and tight end George Kittle warned that McCaffrey cannot be expected to "be the saviour".

"He's not going to be the saviour, but he's definitely going to help us out," Kittle said. "I think these next two weeks are going to be huge for Christian to understand our offense and be comfortable out there not to think at all, just go out and run because that's what he's really good at.

"Like I said, penalties, turnovers, giving up big plays on defense, we've got to be better than that. We weren't today. That's how you lose football games."