Martin said Porter would not start but will play as long as he can and won't be under any restrictions.
The 6-10 Porter played only two minutes in the season opener before going out with a back injury.
The Tigers will face the victor of Wednesday night's Vanderbilt Commodores vs. Georgia Bulldogs matchup in St. Louis. Tipoff will be about 30 minutes following the first game of the day, which begins at 1 p.m. ET.
Martin alerted the media of Porter's return Tuesday, with the news eventually broken via SEC Network's Paul Finebaum.
"Unless Mike says otherwise, that's what it is", Martin said.
Martin said Porter, the No. 1 recruit in the country a year ago, will he able to help Missouri in a variety of ways.
Last month, his doctor cleared him to return to all basketball related activities.