Why hasn’t the Vikings rushing attack, which is on pace to become one of the most punchless in league history, been able to get on track this season?

Sitting at his locker Monday morning, fullback Zach Line slowly shook his head in disbelief for seven seconds before dejectedly saying, “That’s a good question.”

The ground game again got little traction in Sunday’s 26-20 loss to the Washington Redskins. Running back Jerick McKinnon popped a 13-yard run out of the wildcat and wideout Adam Thielen picked up 11 yards and a first down on an end-around. But when they weren’t going backward, the Vikings usually went nowhere.

“It’s just kind of the same story. One guy here and one guy there,” Line eventually said. “We’ve just got to start finishing guys downfield and staying on blocks, helping the runners up after their carries. It’s all the small things. It’s one of those where you just got to get over that thought that we can’t run the ball. We’ve got to believe.”

The Vikings now rank last in the NFL in rushing yards per game at 69.8, falling behind the Giants after New York ran for 122 yards Monday night. In addition, the Vikings have averaged only 2.7 yards per run, more than a half-yard less than anybody else.

And it can’t simply be chalked up to the absence Adrian Peterson, the NFL’s leading rusher last season. He averaged only 1.6 yards per carry in two games before going on injured reserve, though he probably would have popped at least one long run if he were still playing.

It is still unclear whether Peterson, who had surgery to repair a torn meniscus, will return this season. Coach Mike Zimmer again said Monday that he has “no idea.”

The Vikings are on pace to have the lowest yards-per-carry average as a team since the Giants in 1953, three years before Zimmer was born.

Since the 1970 AFL-NFL merger, only three teams have averaged fewer than 3 yards per run over the course of a season — the 1986 and 1994 New England Patriots and the 1992 Indianapolis Colts. The 1994 Patriots, whose leading rusher that year was Marion Butts with 703 yards, were coached by Zimmer mentor Bill Parcells.

The lowest yards-per-carry average in Pro Football Reference’s database, which stretches back to 1940, belongs to the 1943 Brooklyn Dodgers, who went 2-8 with fullback Pug Manders, halfback Merl Condit and the boys mustering only 1.8 yards.

Only 16 teams since 1940 have averaged less than 3 yards per run in a season.

“It’s not all about the average, and we’re trying to fix it,” Zimmer said Monday.

The Vikings’ short-yardage struggles continued at Washington with running back Matt Asiata twice getting stuffed on third-and-1 in the second half, when the Vikings were outscored 12-0.

“It’s unbelievably frustrating,” left guard Alex Boone said in the locker room after the game. “Close game against a good team, converting third-and-1 [wins] that game.”

On 18 occasions this season, the Vikings ran the ball when needing 2 or fewer yards on third or fourth down. They picked up first downs on only half of those plays. Conversely, when throwing it in similar short-yardage spots, they converted 12 of 16 times.

Asiata did score from third-and-goal at the 1-yard line Sunday — w but only after getting stopped the previous two plays, including once with seven linemen on the field.

“That’s going to be one of the big emphases this week, trying to figure this out and get back to being a lot more successful. We should be more successful there,” Zimmer said Monday. “We got knocked back a few times. There were a couple times where we probably should have made it. Anyways, we haven’t gotten it.”

The Vikings finished with 47 yards on 21 carries against the NFL’s 26th-ranked run defense.

And now the Vikings must continue on without left tackle Jake Long, who was lost for the season Sunday because of an Achilles’ tendon injury. They have been hit particularly hard along the offensive line, and Peterson’s top backup, McKinnon, still has not been given a full workload since returning from a sprained ankle that sidelined him one game.

The Vikings are trying not to use injuries as an excuse. But this is their reality.

“Every time it seems like we get it going, we face some more adversity, whether that’s an injury or something else,” Line said.

“We’ve had a lot of obstacles to overcome. It’s hard when you don’t have guys staying healthy all of the time.”