Chip Kelly's offense with the 49ers is his slowest-paced version of his four NFL seasons.

Why?

“I think that’s what fits with this group of guys we have on the offensive side of the ball,” Kelly said this week.

Kelly did not expound on that thought. But it could be safe to assume his thinking is the same reason why it does not make sense to enter a Ford Pinto to race against pro stock dragsters.

The 49ers’ offense is running more plays this season. The 49ers snap the ball every 24.4 seconds on offense. That’s down from 26.1 seconds last season, and 29.7 seconds in Jim Harbaugh’s final season in 2014.

Last season in Philadelphia, Kelly’s team snapped the ball every 22.6 seconds. In Kelly’s final season at Oregon in 2012, the Ducks snapped the ball every 20.5 seconds.

“I don’t think we’re playing fast right now,” Kelly said. “So if someone said, ‘How are you playing offensively?’ I don’t think we’re playing fast offensively. I think we’re just not going back (to huddle). We’re saving seven yards of run time for our offensive line because they don’t have to run back in the huddle, get a play called and then do it.

“We’re just calling it at the line of scrimmage. So I think it’s a lot of what Denver used to do when Peyton (Manning) was there. But there’s a lot of times that we’re under 15 seconds when we’re snapping the ball and getting the play off. So we’re not playing fast and we’re not calling tempo-type plays in those situations. We’re just calling plays.”

Kelly said part of the problem is that the 49ers are not converting third downs. The team has a 36.3 percent success rate on third downs, which is actually an improvement over the 30.5 percent success of last season.

But the 49ers’ overall lack of offensive success this season cannot be camouflaged.

The 49ers are averaging just 4.5 yards per play. The 49ers have not averaged fewer than 5 yards per play since 2007, when Alex Smith sustained a shoulder injury and was replaced by Trent Dilfer.

While the 49ers are running more offensive plays than it has in the past, so is the opposition. The 49ers have averaged 64.3 plays per game. The 49ers have defended 69.9 plays per game – only 2.3 more plays than last season but 8.1 more plays than in 2014.

The biggest problem for the offense has been its run defense. The league’s worst run defense has surrendered 185.1 yards per game and is on pace to give up 2,962 yards this season, which would be the most in the NFL since the 1980 New Orleans Saints yielded 3,106 rushing yards.

