Manny Pacquiao, the WBO welterweight title holder, will tread carefully when he faces Joshua Clottey in Dallas on March 13. "Joshua Clottey is taller and bigger than me," Pacquiao said. "He is a former [IBF] champion. I cannot underestimate him." But Pacquiao's trainer, Freddie Roach, said: "I think Manny will be the first to knock him out."