Detroit made the moves Monday, two days before opening the season at Toronto.
Udrih is entering his 13th NBA season. He has averaged 8.5 points and 3.4 assists in his career. He played for the Heat and Memphis Grizzlies last season, averaging 4.7 points and 2.6 assists.
The 6-foot-4 native of Slovenia was drafted in the first round by the San Antonio Spurs in 2004 and also played for Sacramento, Orlando and New York.
McCallum averaged six points a game over three seasons with the Kings, Spurs and Grizzlies.