San Francisco is expected to meet with Harper this week, Miller added, although a separate report from Jon Heyman of MLB Network claims the two sides have already met.
Harper has generated plenty of interest this offseason, but this is the first time San Francisco has been linked to the 26-year-old.
The Giants' involvement comes as a surprise, considering they've spent their offseason reportedly shopping some of their veteran players in Madison Bumgarner, Brandon Belt, Joe Panik, and Evan Longoria.
San Francisco has reportedly been looking for outfield help, but adding Harper would be an expensive endeavor. The 2015 National League MVP is apparently seeking a deal north of Giancarlo Stanton's $325-million contract and reportedly rejected a 10-year offer worth around $300 million from the Washington Nationals in November. San Francisco's 2019 payroll is already exceeding $164.5 million, according to Spotrac.
In 2018, Harper, a six-time All-Star, hit .249/.393/.496 with 34 home runs and 100 RBIs, while also leading baseball with 130 walks.