Troy Polamalu is 32, or eight years older than the Seahawks' Earl Thomas, who was acknowledged as the NFL's top safety a season ago. Polamalu is coming off one of the most disappointing of his 10 NFL seasons, one in which he was on the sidelines more than he was at safety. The absence of one of football's true defensive playmakers didn't hurt the Steelers' No. 1-ranked defense statistically, but it certainly did psychologically. “It doesn't take a rocket scientist to know we're better with Troy Polamalu healthy and on the field,” safety Ryan Clark said. “He's the best we have in this game.” But 2012 certainly wasn't the best of Troy Polamalu, and he knows it. It was the second time in four seasons he missed a huge chunk of a season — a knee injury limited him to five games in 2009 — and it raised questions about how fit he can stay and how well he can play the rest of his career. And how much longer might that career last? “I don't know,” said Polamalu, who is signed through 2014 to a contract that costs the Steelers more than $10 million in cap space each season. “I don't look beyond tomorrow's practice.” Perhaps reflecting a time when playing into the late 30s isn't as uncommon as it once was, he insists that he and wife Theodora haven't discussed when it might be time to look to retirement. “I hope I know (when it's time to quit),” Polamalu said. “I hope I'm not scratching and clawing for a year (hanging on). I hope I can call it quits when I know it's time. But no, we don't talk about.” What he does talk about, and with a measure of enthusiasm, is a transformed defense that shed James Farrior, Aaron Smith, James Harrison, Casey Hampton and Keenan Lewis in the past two years. Polamalu likes incoming players such as safety Shamarko Thomas and outside linebacker Jarvis Jones, and the competition between Jones and Jason Worilds.