Willie Parker: How injury-prone is this guy? Just who are we dealing with here, Tracy McGrady? Grant Hill? Terrell Davis? Do we need to carve out some space in the Gusiness Book of World Records for football fragility? Parker went down in the third quarter with another knee injury during Pittsburgh’s 27-10 victory over Cincinnati last night. Troy Polamalu picked off a pass in the final minute near the end zone to preserve the cover. Chad Johnson mouthed off to Marvin Lewis in a team meeting and didn’t play, further crippling his quest for a 1,000 yard receiving season.