Cincinnati's ace is 9-1 with a 2.90 ERA in his last 17 starts, the only loss coming July 28 to the Chicago Cubs when he left after allowing two runs in the first inning with a sore back. The Reds have won 14 of Harang's last 15 starts and are 22-6 with him on the mound this season.
The right-hander has a 1.85 ERA in his last five home starts, and is 7-2 with a 2.97 ERA in 14 starts at Great American Ball Park this season.
Martinez made four rehab starts, including last Monday when he gave up an unearned run and five hits in six innings for Class-A St. Lucie.
Mets manager Willie Randolph said Martinez threw "crisp, nice and free" and said the throws appeared to be "effortless coming out of his hand."
The right-hander will be on a pitch count of 75 and no more than 35 pitches in an inning on Labor Day.
