San Francisco free agent quarterback Alex Smith will visit with Miami, said a person familiar with the move.
The person spoke to The Associated Press on condition of anonymity because the team has not announced Sunday's meeting.
Manning has been rehabbing in North Carolina following a string of neck surgeries, which led to Indianapolis releasing the four-time NFL MVP.
Smith and Manning have the same agent, Tom Condon.
Several emails to Smith, multiple phone messages to his father have not been returned
The 49ers had been working to re-sign Smith, the No. 1 overall draft pick in 2005 who made a comeback last year under Harbaugh, a former NFL QB in his first year as a head coach in the league.
Smith has acknowledged he was happy with the three-year offer.
"Alex is trying to figure out what he wants to do," 49ers CEO Jed York said last week. "There have been good conversations back and forth."
The NFC West champion 49ers last week signed wide receiver Randy Moss after he spent a year out of football, hoping he will be the dynamic wideout and deep threat he once was.
The 27-year-old Smith threw for 3,150 yards and 17 touchdowns with only five interceptions as San Francisco went 13-3 and made the NFC title game last season after an eight-year playoff drought.
Manning's whirlwind free agency tour officially kicked off soon after he bid farewell to the Indianapolis Colts in an emotional press conference.
AP Sports Writers Teresa M. Walker in Nashville, Tenn., Joedy McCreary in Durham, N.C., Pat Graham in Denver and Janie McCauley in San Francisco contributed to this report.