HOUSTON -- Tom Lawless was named the manager at Triple-A Oklahoma City on Sunday afternoon. Tony DeFrancesco vacated the position when he accepted the interim manager position for the Astros after Brad Mills was let go Saturday.

Lawless began the season as the Minor League roving infield instructor. He has managed at Class A Lexington (2009), Advanced Class A Lancaster (2010) and Double-A Corpus Christi (2011).

"Tom has managed in our system in the past, most recently with our Corpus Christi affiliate last season," said Astros director of player development Fred Nelson. "This move allows us to send an experienced manager to Oklahoma City, while keeping the rest of our field staffs intact."

Before becoming a manager, Lawless serves as an infield instructor for the Orioles from 2006-08. He played in eight Major League seasons with four different teams. His playing career ended in 1990.

Lawless will be with the team before tomorrow's game at Round Rock.

Fernando Martinez has homer reversed on replay

ARI@HOU: Martinez's homer overturned upon review

HOUSTON -- Astros outfielder Fernando Martinez circled the bases in the fourth inning Sunday afternoon after hitting what he believed was his second home run the season, but modern technology spoiled the trot.

Martinez hit a fly ball to left-center field that caromed near the yellow line and bounced back into play for what was initially ruled a home run. D-backs manager Kirk Gibson asked the umpires to take a look at instant replay.

The umpires emerged within minutes and determined Martinez's ball struck below the yellow line, which was a double. Martinez went back to second base and was eventually stranded at third base.