The Diamondbacks optioned left-hander Tyler Skaggs to Triple-A Reno Monday morning, one of five moves that reduced the number of players in big league camp to 39.

"He just wasn't ready and we felt it was being counterproductive with him being here," said D-backs manager Kirk Gibson. "We all talked about it and we thought that was the right thing to do. I think he's a little bit relieved, to be quite honest with you. We'll get him back on track."

Skaggs, who had been competing with Patrick Corbin and Randall Delgado for the final spot in Arizona's rotation, struggled in Cactus League play. In four appearances (two starts), Skaggs went 0-2 with an ERA of 11.00 in nine innings of work.

Control was also a bit of an issue as Skaggs walked eight batters while striking out five.

"He knows what he's doing," Gibson said. "How do you stop it when you go out and you're trying to win a job with every pitch? It's kind of hard when you get into bad habits.

"Hopefully he'll relax a little bit (in Triple A) and throw the baseball the way he's capable."

Skaggs was ranked as the top lefty pitching prospect heading into the season by Baseball America, and the 12th-ranked overall prospect.

Infielder Kila Ka'aihue, left-handed pitcher Rommie Lewis, catcher Rossmel Perez and outfielder Brad Snyder were also reassigned to Arizona's minor league camp.