Matzek (elbow) signed a minor-league contract with Atlanta on Saturday and will report to Triple-A Gwinnett.
The Giants released Matzek (elbow) on Friday, Alex Pavlovic of NBC Sports Bay Area reports.
Matzek (elbow) began a rehab assignment at Triple-A Sacramento last week and has given up two runs (one earned) on one hit and one walk while striking out a batter across two innings over his two appearances.
Matzek (elbow) has been playing catch from 90 feet, Mark Bowman of MLB.com reports.
Atlanta transferred Matzek (elbow) to the 60-day injured list Tuesday, Grant McAuley of 929 The Game reports.
Atlanta placed Matzek on the 15-day injured list Tuesday, retroactive to May 5, with left elbow inflammation, Grant McAuley of 929 The Game reports.
Matzek gave up two runs on three hits in the eighth inning of Thursday's loss to the Mets.
Matzek touched 95 mph with his fastball during Sunday's Grapefruit League appearance, David O'Brien of The Athletic reports.
Matzek (side) struck out two over a scoreless inning Thursday in Atlanta's 3-1 loss to the Rays in Grapefruit League play.
Matzek (side) is expected to return to Grapefruit League play in the next few days, Mark Bowman of MLB.com reports.