Running back is a mess right now in Green Bay.

As if the Packers’ offense didn’t have enough problems already, now it will be without starter Eddie Lacy until at least Week 15.

Hours prior to Green Bay’s Thursday Night Football game against the Chicago Bears at Lambeau Field, the team announced it had placed Lacy on injured reserve. Multiple reports indicated he will have surgery on his left ankle, which he sprained and then played through in Sunday’s loss to the Dallas Cowboys, when he was the only active halfback and gutted out 65 yards on 17 carries.

The Packers are expected to wait until after the operation to decide if they want to use the designated-to-return tag on Lacy, allowing him to come back in eight weeks, but they reportedly plan to do so.

This is just the latest – and most significant – injury hit for Green Bay, which earlier this week placed top cornerback Sam Shields on IR and has ruled out seven players for Thursday night’s divisional showdown. With backup James Starks also unavailable after undergoing knee surgery, the Packers are now missing the only two running backs with which they started the season.

So, um, who’s going to carry the ball for Green Bay?

After the nightmarish backfield situation against the Cowboys, the team on Tuesday acquired Knile Davis in a trade with Kansas City, sending a conditional late round draft pick to the Chiefs in exchange for the expendable fourth-year back. Davis, the first player that general manager Ted Thompson has traded for since 2010, has some experience and lots of speed, having run the 40-yard dash in 4.37 seconds in 2013.

However, this season he’s only carried one time for minus-2 yards and in the last two years has just 29 rushes for 70 yards. After arriving in Green Bay on Tuesday morning, Davis (5-foot-10, 227 pounds) will have had about 48 hours to prepare for the game against the Bears and is only expected to get a handful of running attempts.

The guy who will get the bulk of the opportunities figures to be undrafted rookie Don Jackson, who was promoted on Thursday from the practice squad. He’s expected to start in the backfield for the Packers, despite having not yet taken an NFL snap – he was sidelined for all of the preseason due to injury.

Jackson (5-10, 208) was considered a high-effort runner in college, when he gained 2,318 rushing yards on 520 carries in three seasons at Nevada. He’s not big or terribly fast – though a reported 4.47-second 40 time at his Pro Day somewhat belies that reputation. But he could be a goal-line option for Green Bay, and at his size, it’s also easy to see him shooting through the substantial holes the Packers’ offensive line has been creating in recent weeks.

The Lacy injury was terrible news for a team already lacking running back depth, but its implications are hardly surprising. Thompson kept three running backs on the season-opening 53-man roster, but almost immediately released third-stringer Brandon Burks in order to sign long-snapper Brett Goode on Sept. 5. Starks played in the first four games but was ineffective, gaining just 42 yards on 24 carries (1.8 average) with a fumble, before suffering a knee injury. He had surgery on Sunday and is expected to be out at least four weeks.

Despite knowing it would be without Starks, Green Bay did not make a move to bolster the backfield before last week’s game against Dallas. Instead, it rode a gritty, leaping Lacy, even as he appeared to be in obvious pain, supplementing him with wide receiver Ty Montgomery, who was used as a running back and rushed three times for six yards. Montgomery, who showed his ability as a check-down pass-catcher with 10 receptions for 98 yards in Week 6, is expected to be utilized a bit in that role again Thursday night. As Lacy, who is averaging an impressive 5.1 yards per carry this season, hobbled off the field after runs, it was clear he was exacerbating the ankle by playing on it.

On Monday, head coach Mike McCarthy gave the first clue that Lacy’s injury was more serious than first thought, mentioning that the big man was "very sore" and wouldn’t practice Tuesday, despite the short week. Desperate for depth, Thompson made the rare trade for Davis – who is a gifted kick returner and may be able to contribute immediately on special teams – and two days later signed Jackson to the active roster. Besides Montgomery, wide receiver Randall Cobb could also see some snaps as a running back. Fullback Aaron Ripkowski, who took over the job from departed veteran John Kuhn, isn’t as much of a rusher as his predecessor.

The current chaos in the backfield, due in part to front-office unpreparedness and then plain old bad luck, is symptomatic of the general offensive disorder in Green Bay. Quarterback Aaron Rodgers ranks 20th in the NFL in passer rating, 26th in completion percentage and 26th in yards per attempt; his receivers have struggled to find separation and get open, and his coach continues to take criticism for unimaginative and conservative play-calling. The Packers are 25th in yards per game (331.8) and 17th in points per game (22.8).

After the ugly display last week, Green Bay could really use a bounce-back offensive performance against Chicago. The Bears have a mostly healthy 11th-ranked defense, which is allowing 233.5 passing yards (No. 10) and 107.7 rushing yards (No. 19) per game.

Will this be the game the familiar, high-powered Packers offense returns, or will the issues at running back prevent it from, once again, playing like the one fans know and expect?