Teenage sprinter LeShawn Merritt's coach is confident the American will run the 400 metres in under 44 seconds this summer, a feat accomplished by only seven men. "To think that he could break 44 is very realistic," veteran coach Bill Carson said. The 18-year-old world junior 400 metres champion outdoors, shocked indoor fans when he ran the distance in 44.93 seconds in Arkansas on Friday, a time only world record holder Michael Johnson has beaten. Johnson set the indoor record of 44.63 seconds in 1995 and ran 44.66 a year later.