Pat Riley once guaranteed his Los Angeles Lakers would win a second straight title. After they did so in 1988, Lakers star Magic Johnson put a towel over his coach’s face to make sure he wasn’t going to guarantee a third. As it turned out, the Lakers fell short of getting there. But 25 years later, a Riley team will have another chance. The Miami Heat, put together by team president Riley, won their second straight crown last Thursday, Now, they’ll head into next season seeking a three-peat, a term Riley actually has trademarked. Guard Dwyane Wade didn’t guarantee Monday after the latest victory parade his Heat can reach that goal. But he sure didn’t mind putting it out there. “Magic Johnson, he’s got five rings and he never won three in a row,’’ Wade said. “So that shows how tough it is. But we’re going to throw our hat in the ring and see with what we come out with. We’re going to be back next year hungry again to try to continue to place ourselves in history. Winning back-to-back is special. Winning back-to-back-to-backs would be something out of this world. “We’ll cross that bridge when we get there. But obviously this summer, once we start focusing back on the game of basketball, that’s going to be our goal. How do we come back and muster up enough to keep us focused, to keep us hungry throughout the season to get ourselves back in a position to win another championship?’’ Considering what Wade went through this postseason, finding motivation shouldn’t be a problem for him. Wade played gallantly on a pair of wobbly knees.