Kemp has intensified his recent spring workouts, which have included running and tracking fly balls in the outfield.
Although Kemp will not play in the Dodgers' regular-season opener in Australia, Mattingly thinks the two-time outfielder has gotten closer to a return to game action.
"We're seeing him take fly balls, getting jumps," Mattingly said Saturday, according to MLB.com. "He's swinging the bat good. It won't be long before he's in a game."
Mattingly acknowledged that he was uncertain whether Kemp would play in a spring game before the Dodgers' March 16 flight to Australia, where they will take on the Arizona Diamondbacks in a two-game series on March 22-23.
"I don't put that kind of timetable on it," Mattingly said. "As long as he's moving forward."
Kemp, 29, underwent surgery on his left ankle in October following an injury-plagued 2013 season, when he batted .270 with a career-low six home runs in just 73 games.
Kemp, who signed an eight-year deal worth $160 million following the 2011 season, has appeared in just 179 games over the last two years.