The Astros originally said they would wait until Tuesday to promote their September callups, but they got the ball rolling early when they summoned right-handers Jack Cassel and Fernando Nieve from Triple-A Round Rock Monday. Both pitchers were in uniform for the Astros' series opener at Wrigley Field.
After the game started, the Astros announced three additional callups who will join the team Tuesday in Chicago: right-hander Alberto Arias, catcher J.R. Towles and infielder Edwin Maysonet. Arias and Towles were already on the 40-man roster, and Maysonet's contract was purchased from Round Rock prior to adding him to the roster
From here
Prior to Tuesday's game at Wrigley Field, the Astros activated second baseman Kazuo Matsui from the 15-day disabled list and outrighted right-hander Runelvys Hernandez to Triple-A Round Rock.No real comments... I wouldn't expect to see much of any of these players (besides Kaz) unless the Astros lose a couple of games.
From here