The Reds selected Phillips' contract from Triple-A Louisville ahead of his scheduled start Monday against the Twins.
He'll be making his third start of September with the Reds after posting an 8.31 ERA and 1.85 WHIP in 8.2 innings between his first two big-league outings. After Monday, the Reds will be able to get by with a four-man rotation for the rest of the season as they look to chase down a playoff spot, so Phillips could be a candidate to return to Triple-A immediately after the start.