LONG POND, Pennsylvania — Tony Stewart lost his pole position and will start from the back of the pack after wrecking his car during practice for the Pennsylvania 500 on Saturday.Stewart lost control of his No. 14 Chevrolet on a turn on the second lap of Saturday's first practice and spun into the wall. He was unhurt in the crash.His Stewart-Haas Racing crew quickly got to work on the backup. Stewart leads the points standings and was the pole sitter at Pocono because rain washed out Friday's qualifying."I just screwed up," Stewart said. "I got in too deep and got loose and couldn't save it."The same scenario happened to Stewart in June's race at Pocono when he took the pole after a rainout and wrecked in practice. Then he went out and won on Sunday in his backup from the rear of the field.He'll have to pass 42 other cars again to really duplicate the feat."I know we can do it," Stewart said. "I tore up a really good race car today."Stewart, 192 points ahead of Jimmie Johnson in the points standings, is one of four drivers to win a Cup race this season from the rear of the field. He's trying to become the third driver since 2004 to sweep the two Pocono racesStewart's June win at Pocono made him the first owner/driver to win a race since Ricky Rudd at Martinsville in 1998.