NBA.com later confirmed the report.
McGrady, who is 33 years old, hasn't played in the NBA since May 10 of last year. He was last rostered on the Atlanta Hawks, playing 52 games in the 2011-12 campaign. He averaged 5.3 points, 3.0 rebounds and 2.1 assists in 16.1 minutes per game off the bench.
Without any NBA offers following the conclusion of the lockout-shortened season, McGrady signed with the Qingdao Eagles of the Chinese Basketball Association in October of 2012. Though he experienced some early hiccups with the team, he finished the CBA season with impressive averages of 25.0 points, 7.2 rebounds and 5.1 assists in 29 contests.
McGrady is a seven-time All-Star and two-time NBA scoring champion. In his prime, he was compared to some of the greats of the game, but injuries have diminished his performance over the last several years.
For his career, McGrady has averaged 19.6 points, 5.6 rebounds and 4.4 assists. He has also registered a career PER of 22.13, good for 28th in NBA history, according to Basketball-Reference.com.
The Spurs will be the seventh team he's joined since being drafted by the Toronto Raptors in the first round of the 1997 NBA draft. His signing comes after San Antonio waived swingman Stephen Jackson on April 12.
It will be interesting to see what McGrady can contribute to the Spurs with the playoffs around the corner, but considering coach Gregg Popovich's ingenuity, he will likely carve out a role with the Western Conference's two seed.