Eagles cornerback Brandon Boykin isn't hard to find in the Eagles defensive backfield. If you can't see No. 22, just look for the guy who's head ends much lower to the ground than the other cornerbacks.
Boykin stands at 5-foot-9, a miniaturized version of the Eagles' tree-sized corners, Nnamdi Asomugha (6-foot-2) and Dominique Rodgers-Cromartie (6-foot-2). Not that one needs to be tall to be an effective corner - in fact, Boykin's quickness and ability to work within traffic make him a solid nickel corner.
His lack of height, though, could make him more vulnerable for deep passing when covering the slot receiver.
And the Steelers' slot receiver can get open deep.
Emmanuel Sanders was the X (wide on the line) receiver in the Steelers offense when Mike Wallace sat out training camp and the preseason. His combination of height and speed give him that advantage over positional players who are not routinely as big as the ones playing cornerback in Philadelphia. With Wallace back at the X, Sanders can be seen doing damage in the slot. He has 10 catches on 16 targets this season, and is averaging over 12 yards per catch.
The size and strength brought from Asomugha and Rodgers-Cromartie - they're almost assuredly covering Wallace and Antonio Brown Sunday, oftentimes in man-to-man press coverage - give them an advantage over smaller receivers and allow them to withstand the strength of bigger ones. The viability of Sanders making plays within this offense could convince the Eagles to not attack as much in man coverage, which would put them off their game.
The real trick here - and the main thing to watch - is how Steelers offensive coordinator plans to use his tight ends. The Eagles defensive ends, Trent Cole and Jason Babin, line up even further than the traditional base 4-3 defensive ends line up. In what's called "Wide Nine," the ends are in four-point stances at the outside shade of the tight end - or, the 9-technique - looking to out-flank the protection, and get even with the slower-footed tackle before the typically bigger and stronger tackle can get his hands on him to redirect his path.
With a possible mismatch advantage for the Steelers in their three wide receiver packages, they would have to surrender the ability to get an immediate hand on both of the wide-9 defensive ends by only using one tight end.
The Steelers aren't likely to play three wide receivers exclusively, even if they don't use two tight ends all that often. When Sanders is on the field, though, in the slot, it will be interesting to see how the Eagles choose to defend them - in man or zone. If they read man, look for Sanders to run routes behind the linebackers' drops.