Boston Celtics center Daniel Theis just secured a two-year, $10 million deal to return to the team. However, he will need to prove that he can contribute significantly next season, as only one year of his contract is guaranteed.

The Celtics essentially have a team option on Theis' contract, and they can pick it up or walk away from it on a specific date next year:

Theis played in 66 games for the Celtics last season, averaging 5.7 points and 3.4 rebounds in roughly 14 minutes of action per game. The German will likely start the season as the second-string center behind Enes Kanter.

Theis has shown potential to be a decent big man in the NBA. The 27-year-old can become an integral part of the Celtics' future if he keeps improving. Avoiding injuries is also another way for him to secure the second year of his deal.

The Celtics have chosen a reasonable date to guarantee Theis' contract, as July 3 is right in the middle of the moratorium. If Boston needs to make room for a better player, it would be easy for them to let him go. However, if the Celtics really like Theis' contributions or if they simply don't need extra cap space for another move, they can easily just keep him.

This is a low-risk, potentially high-reward deal for Boston.