"Tackling running back Brandon Jacobs of the New York Giants, who is 6-foot-4 and weighs 264 pounds, may be like knocking down a run-away piano.

But Steelers safety Ryan Clark would opt to stop Jacobs rather than Chargers' running back Darren Sproles, the smallest man in the NFL at 5-6 and 185 pounds.

Sproles can embarrass would-be tacklers.

"With guys like Sproles, you never know," Clark said. "One minute they're right in front of you, and then they're three, four yards away with one cut. It is extremely hard to play against those guys."

The Steelers and Chargers will both rely on average-sized men when they clash tonight at Heinz Field.

For the Steelers, rookie return specialist Stefan Logan, who is the same height as Sproles, has added a new dimension for the defending Super Bowl champions. He has just missed touchdowns with kickoff returns of 59 and 39 yards so far this season.

Sproles and Logan are among the handful of shorter players who are succeeding at football's highest level. Their speed and elusiveness give defenders fits. Then there is the height factor.

Clark, who is 5-11, said he has trouble getting low enough to tackle players such as Sproles and Logan. Imagine how difficult it can be for Steelers defensive end Brett Keisel, who stands 6-5.

"I've gotten several times where I've hit Sproles and Stefan, and it knocks the wind out of you," Keisel said. "You're basically just running up there and hitting them with your stomach. It definitely brings a different element to the game. Those little guys are hard to grab onto — like chasing a rabbit around. It's hard.""