Haven’t we seen this before? Ben Roethlisberger gets carted off the field Sunday. (Justin K. Aller/Getty Images)

It’s not clear for the Pittsburgh Steelers whether Ben Roethlisberger’s immense toughness is a virtue or a flaw. Sunday afternoon, on a day another quarterback might not have been playing at all, Roethlisberger crumpled to the ground after taking a sack and grabbed his left leg. He had to be helped off the field, and later he was transported to the hospital for tests on his left foot, a troubling indication that Roethlisberger had suffered his second serious injury of the season.

Even though backup Landry Jones engineered a last-minute scoring drive to lift the Steelers to a 38-35 victory over the Oakland Raiders, the Steelers’ hard-luck season could wither should Roethlisberger miss another handful of weeks. They may wonder if Roethlisberger returned too quickly from a left knee injury. They may wonder if Roethlisberger is too tough for his own good.

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In Week 3, Roethlisberger’s left knee bent at a nauseating angle. He avoided a serious injury and was diagnosed with a ligament sprain, which would sideline him for four-to-six weeks. He returned after four, of course, but only after flirting with playing after three weeks. It’s too soon to do anything but speculate if Roethlisberger’s knee injury has any correlation to the foot injury he suffered Sunday. It’s possible though that Roethlisberger may have made himself more vulnerable by returning so soon.

Roethlisberger absorbs punishment without blinking, an admirable trait for any football player but a dangerous quality for a franchise quarterback. He has been conditioned to believe defenders will always take the worst of a collision. Hitting him is like running into a slab of drywall. He can take a beating, and so he does. It helps make him one of the best quarterbacks in football, but it also endangers him.

The Steelers already must play the rest of the season without Le’Veon Bell, who tore ligaments in his knee last week as Roethlisberger returned. Jones, in his third season out of Oklahoma, put up a 93.2 quarterback rating in two games before Sunday and helped the Steelers win Sunday after Roethlisberger’s exit.

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The Steelers aren’t necessarily done even with their raft of key injuries. If Roethlisberger misses extended time, Jones will have the security of throwing to Antonio Brown. On Sunday, Brown caught 17 passes for a preposterous 284 yards and made the reception that set up Pittsburgh’s game-winning field goal.

The Steelers have withstood Bell’s absence with DeAngelo Williams, who stands as one of the smartest offseason additions in the league. Williams filled in for Bell as Bell served a two-game suspension at the outset of the season. In his place Sunday, Williams gained 225 yards on 27 rushes and two receptions.

The Steelers’ offense can put enough pieces around Jones to remain competitive, and maybe even to sneak into the playoffs. But Pittsburgh needs Roethlisberger if it wants a realistic chance to make any meaningful noise this season. They will have to wait and hope. They can only wonder if Roethlisberger’s best attribute is also his greatest weakness.

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