Summary
At the start of the '19-'20 season, Wagner was on fire from three, looking like a legitimate pick-and-pop threat for a Wizards team that was all offense and no defense. However, Wagner started to cool off as the season went on, and the Wizards realized how harmful having a big that was as poor defensively as Wagner was to their chances of winning. The Wizards declined the fourth year team option on Wagner's rookie scale contract, and he was traded to Boston in '20-'21, where he was waived by the Celtics and ultimately signed with Orlando, who subsequently drafted his brother, Franz.

Wagner had a renaissance in Orlando, beating out Mo Bamba as the primary back-up center, and has performed adequately in that role. While Wagner is not the most athletic player, plenty of bigs have learned to overcome their athletic limitations on defense through positional awareness and disciplined verticality. Those kinds of bigs that can protect the rim can stick around in the league, even if they can get picked apart at times by being forced to defend in space. Wagner has been able to make up for some of his limitations by simply playing hard.

If Wagner can get to an above-average percentage from three, he could be a solid outside threat in the same manner of Kelly Olynyk or Mike Muscala. Wagner has only hit 32% from three over the past few seasons, but has still found ways to be effective through playing hard on both ends. He has finished decently at the rim, and the personal dynamics of having him in Orlando also works well for his hopes of sticking in the league.
 
Cap Considerations
Wagner has a $8 million team option for 2024-2025, and if the Magic decline that option he will be an unrestricted free agent with a $15.2 million cap hold and full Bird rights. As his cap hold exceeds the salary he will get in free agency, his cap hold is not really relevant. 

If the Magic re-sign Wagner, his cap hold will be replaced by his starting salary, and the Magic may still have some cap space available depending on his salary and what happens with their other free agents. If the Magic need to maximize their cap space, they could decline his option but re-sign at the same amount of his team option by re-signing him using the Room Mid-Level Exception after using their cap space. There's also a chance that the Magic operate over the cap in 2024 and retain their own free agents while having the full Non-Taxpayer MLE and the Bi-Annual Exception to add players.

Depending on how close the Magic are to the luxury tax after free agency (or on how much cap space they need), if Wagner is brought back by the Magic on a multi-year contract they could benefit from frontloading his contract, as it could give them additional flexibility in the future.

If Wagner hits free agency, other teams will have multiple ways to sign Wagner as even teams without cap space could use either the Non-Taxpayer MLE, Taxpayer MLE, or possibly even the Room MLE or Bi-Annual Exception to sign him. It's also possible that Wagner only gets offers for the minimum.