In Shamarko Thomas, the Steelers hope they have found the next Bob Sanders, a compact, powerfully built safety who delivers torpedo-style hits. They hope he is not the next Anthony Smith. Thomas is a 5-foot-9, 213-pound bundle of speed and unbridled power, and the Steelers thought enough of him to do something they rarely do -- trade away a future draft choice. And the decision, strangely enough, was based on draft choices they don't have. At least, not right now. "He's not the biggest kid, but he certainly doesn't play that way," general manager Kevin Colbert said. "He leaves it on the field." The Steelers needed a safety because they have little depth behind Troy Polamalu and Ryan Clark after backups Will Allen and Ryan Mundy signed elsewhere in free agency. In addition, Clark is 34 and Polamalu could be facing the same situation in 2014 that James Harrison did this year if he doesn't have a more significant impact on the defense. Polamalu missed nine games last season because of injuries and finished with just one interception and no forced fumbles or fumble recoveries. So the Steelers traded their third-round choice in 2014 to the Cleveland Browns to draft Thomas with the 111th overall selection -- four spots ahead of their own fourth-round choice. It was the first time since 1973 the Steelers traded a future draft choice, but they did it because they expect to get third- and fourth-round compensatory picks in 2014 for Mike Wallace, Rashard Mendenhall and Keenan Lewis. "We viewed him as valuable as a third-round pick would be," Colbert said. Pitt fans will remember Thomas for his vicious helmet-to-helmet hit on tight end J.P Holtz in a game at the Carrier Dome last season -- a play in which Thomas' helmet went flying off his head and he immediately collapsed to the ground. The play happened in the fourth quarter, and Thomas never returned to the game.