There has been speculation that Carlos Zambrano could replace Jonathan Pettibone in Philadelphia's starting rotation.
However, Ruben Amaro Jr. said Sunday that Zambrano was not ready to pitch in the majors.
"Not based on what I saw his last outing, not in my mind," Amaro said. "I'd like to see him pitch again [in the minors]. We'll keep a close eye on his starts and how effective he is. But he's not ready yet in my mind."
The Phillies signed Zambrano in mid-May to provide organizational depth following injuries to Roy Halladay and John Lannan.
Zambrano has made four official starts, two in Single A, one at Double A and one at Triple A.
In 21 1/3 innings, he has allowed 14 hits and three earned runs, but he has walked 11 while striking out 17.