DALLAS The summer just keeps getting brighter and brighter for the Dallas Mavericks.On Monday, the Mavs added yet another quality piece to their off-season puzzle when they agreed to a contract with Memphis Grizzlies shooting guard O.J. Mayo. The 6-foot-4 Mayo averaged 15.2 points, shot 43.3 percent from the field and 37.5 percent from 3-point range during his four-year career with the Grizzlies, who made him the third overall pick in the 2008 NBA Draft.It was Mayo who announced to the world, via his Twitter account, that hes joining the Mavs. Mayo tweeted: I will be signing with Dallas! #Mavsnation.Not long afterward, owner Mark Cuban tweeted: Welcome to the family OJ. We are fired up!! MFFL Mavs/Mayo Fan For Life!The acquisition of Mayo, 24, nearly completes a very busy off-season for the Mavs.The Mavs missed out on free agent point guards Deron Williams (Brooklyn Nets) and Jason Kidd (New York Knicks), and lost shooting guard Jason Terry (Boston Celtics) to free agency. But general manager Donnie Nelson and Cuban were able to acquire center Chris Kaman (1 year, $8 million), point guard Darren Collison (1 year, $2.3 million), shooting guard Dahntay Jones (1 year, $2.9 million) and forward/center Elton Brand (1-year, $2.1 million).After all the wheeling and dealing, the Mavericks still had approximately $4 million in salary cap space they could use to sign a player of Mayos caliber. And that likely was more than enough for Mayo, who became an unrestricted free agent when the Grizzlies refused to pick up his $7.2 million qualifying offer.The addition of Mayo gives the Mavs 10 players under contract, including Dirk Nowitzki, Shawn Marion, Vince Carter, Rodrigue Beaubois, Dominique Jones, Kaman, Brand, Collison and Jones. The Mavs also have a team option for center Brandan Wright at $947,907, and could re-sign free agent point guard Delonte West.Rookies Jared Cunningham, Bernard James and Jae Crowder all could wind up making the final roster next season.The 6-4 Mayo, who made $5.6 million last season, could step into the starting lineup with Nowitzki, Marion, Kaman and Collison. Also, the off-season moves still allow the Mavs to be a major player during next summers free agency period that could include Chris Paul, Andrew Bynum, Dwight Howard, James Harden, Josh Smith and David West.