Those defensive backs invited to the combine workouts arrived in Indianapolis on Saturday, and team scouts, coaches and medical personnel will begin poking and probing them today. The Steelers will have a front-row seat and will pay close attention when they parade the safety candidates around the room. No team had stronger safeties than did the Steelers in 2011 when Troy Polamalu made his annual trip to the Pro Bowl following that season and Ryan Clark joined him for the first time. A year later, neither made it to the all-star game, and this year Polamalu will be 32 years old and Clark 34. It's time for the Steelers to find their replacements. Clark enters the final season of his contract and while he played at a Pro Bowl level last season, he's not getting any younger. Polamalu, on the other hand, is not getting any healthier. He missed nine games with a calf injury last season and has missed 22 over the past four seasons with injuries.