NFL.com's Ian Rapoport gave the specifics on Jackson's thigh ailment on Twitter:
More not-so-great news for the #Falcons? RB Steven Jackson (thigh) may miss 2-4 weeks, source says. Officially viewed as week-to-week though— Ian Rapoport (@RapSheet) September 17, 2013
Jackson ran three times for no yards against the Rams in Week 2. However, he did catch an eight-yard touchdown in the first quarter.
In a Week 1 loss to the New Orleans Saints, Atlanta's free-agent acquisition ran the ball 11 times for 77 yards, which included a 50-yard scamper in the third quarter.
Jackson was brought in to add some punch to the Falcons' rushing attack that averaged 3.7 yards per carry in 2012—tied for 28th in the league.
While general manager Thomas Dimitroff certainly shouldn't be criticized for moving on from plodder Michael Turner, Atlanta was just a few plays away from a Super Bowl berth last year without an efficient running game.
According to Football Outsiders, the Falcons finished the 2012 season seventh in yards per drive, eighth in touchdowns per drive and fifth in points per drive.
Ryan threw 615 passes and, as a team, Atlanta ran the football 378 times, which equated to the Falcons throwing the ball on 61.9 percent of their offensive plays.
Only six teams were "pass-happier" than the Falcons and, interestingly, they were the only playoff team of the top 10 in this category.
Here's a look at Turner's efficiency last season:
That stark contrast doesn't tell the entire story.
Sure, the Falcons may have benefited from a more potent running game in their four defeats of the 2012 campaign, but Turner's ineffectiveness wasn't the reason they lost.
In eight of Atlanta's 14 wins last season, Turner averaged less than 3.5 yards per carry.
Last year proved that as long as Ryan's passing game is clicking, the Falcons shouldn't need much productivity from their running game.
However, the more specific reason Atlanta may have signed Jackson was to play the role of a clock-eating closer in the second half of games—especially after what happened in the playoffs.
The Falcons squandered a 20-point lead in the divisional round against the Seattle Seahawks before narrowly escaping with a win, and they were up 17-0 and 24-14 at the half before losing to the San Francisco 49ers in the NFC Championship Game.
Then again, here's a look at some of Jackson's splits from a year ago:
From those numbers, and based on the Falcons' simple, yet logical desire to bolster their running game, Jackson was likely seen as an ideal back for their predictably pass-heavy offense as long as he was kept relatively fresh until the third and fourth quarters.
Without him, Jason Snelling and Jacquizz Rodgers will take over the complementary role in Atlanta's offense.
Before the 2013 season began, Rodgers' career average was 3.75 yards per carry and Snelling's was 3.93.
Clearly, neither is an explosive or necessarily dependable option, but we must not forget that Turner averaged a mere 3.6 yards per carry in 2012.
On the pass-blocking front, Turner was one of the NFL's best at his position, as Pro Football Focus (subscription required) gave him a plus-2.8 rating in that department last season. Fortunately for Smith's club, Rodgers was given an even better rating of plus-3.3.
The Falcons will be tested in Miami against a stingy, underrated Dolphins defense in Week 3 and host the New England Patriots in Week 4 before a Monday Night Football outing at home against the New York Jets in Week 5.
Atlanta won't be as good offensively without Steven Jackson, but the impact of his absence will be barely discernible.