Tim Duncan admitted he had hesitation before opting into his $10.3 player option for the 2014-15 season.

“There was some hesitation there,” Duncan said.

Ultimately, Duncan did not want to leave a season on the table.

“It came down to, I'm not going to be able to do this again,” Duncan said. “So as long as I'm feeling I can (play), and I feel good about it, this is where I want to be.”

Free agent center Aron Baynes has re-signed with the San Antonio Spurs on a fully guaranteed, one-year contract, a league source told RealGM.

Baynes held an extensive negotiation with the Spurs throughout the NBA offseason while also fielding interest in China and Europe. There had been question within the Spurs about their ability to re-sign Baynes, and the team pursued Gustavo Ayon earlier in the month offering a partially guaranteed deal, sources said.

The Spurs signed Baynes to a deal for more than his league minimum, a source said.

In playing 53 games in his second season for San Antonio, Baynes averaged three points and 2.7 rebounds in 9.3 minutes a game. When given extended minutes, the 27-year-old intrigued the front office with his post talent.

The 6-foot-10 Baynes also played for the Australian national team this summer, averaging nearly 17 points and seven rebounds in the World Cup of basketball.

Sean Marks will return to the San Antonio Spurs' front office as an assistant general manager, the team announced Tuesday.

In addition, Brandon James has been promoted to director of basketball administration and legal affairs, Phil Coles has been hired as director of medical services and Marilyn Adams as director of rehabilitation.

Xavi Schelling joins the Spurs as applied sports scientist and Paul West has been named assistant athletic trainer.

Marks was an assistant coach under Gregg Popovich last season.

Gustavo Ayon has signed with Real Madrid.

Ayon also had offers from the San Antonio Spurs and in China.

Ayon had an impressive World Cup after spending last season with the Atlanta Hawks.

The Shanghai Sharks are making a strong push to sign Aron Baynes.

Baynes is currently a restricted free agent of the San Antonio Spurs.

The Spurs would retain Baynes' restricted free agent rights if he signs abroad.

Gregg Popovich made sure the San Antonio Spurs used their 2013 NBA Finals defeat as motiviation, but he faces the opposite problem now.

“I'm worried for one reason,” Popovich said. “They are human beings. They are going to feel satisfied.”

The Spurs defeated the Miami Heat in five games for the championship last season. Miami stole Game 2 on the Spurs' home court before losing three in a row.

“When they won Game 2,” Popovich said, “they probably didn't handle that win real well. They were probably thinking that we got lucky in Game 1, with the air conditioning issue, and they thought they were just going to do it again. As two-time defending champs, it was natural. This had become their place in the world.”

The Spurs rebounded from losing Game 2.

“There was a different mantra,” Popovich said. “Boarding the plane, before practices, during shootaround, we said, 'We came here to win two.' We totally believed at that point. We thought we were better.”

Gustavo Ayon has received a formal offer from the San Antonio Spurs, sources tell RealGM.

Shandong of the Chinese Basketball Association has also presented a formal offer to Ayon, sources confirm to RealGM.

Ayon has previously received offers in Europe, though the language of the contract concerning an NBA out held up an agreement being reached.

Ayon is now deciding between three formal offers.

Ayon spent last season with the Atlanta Hawks.

Michael Beasley is working out for the San Antonio Spurs this week.

Beasley had workouts for several teams this offseason, including two with the Los Angeles Lakers, but he remains a free agent.

Beasley spent last season with the Miami Heat.

The Spurs have an open roster spot as they continue to be unable to sign restricted free agent Aron Baynes.

The San Antonio Spurs are taking a more active involvement in the development of unsigned players whom they own the draft rights for in the NBA.

The Spurs have sent an assistant to work with Livio Jean-Charles.

"David was sent by the Spurs, and he will be present throughout the year," said Jean-Charles in an interview with BeBasket. "He is here to witness but also be involved with my season here. But I want to be clear, Peter Vincent is in charge of my evolution at ASVEL."

Tony Parker partially owns ASVEL.

The Spurs also played a role in setting a timetable for Davis Betrans' return from injury. Betrans was a 2011 draft pick of the Spurs, but he has no contractual obligations to the team.

The San Antonio Spurs are open to signing-and-trading Aron Baynes, according to source.

Baynes is coming off a strong World Cup for Australia.