Summary
Age has not been kind to the former All-Star. As Teague has lost some quickness, it really has hurt his ability to be effective on offense. In his prime, Teague was dynamic getting into the lane for floaters or getting all the way to the rim. Now, Teague struggles to put pressure on the defense by getting downhill.

He was never a high volume shooter from outside, and has become even more gun-shy over the years. While he shot a career best 44% from three this season, it was on very low volume. Teams can go under screens and not worry about Teague hurting them from outside. Teague signed in Boston for the minimum last offseason, and it looks like he'll likely be on minimum contracts for the rest of his career.
 
Cap Considerations
Teague will be an unrestricted free agent with a $1.7 million cap hold and Non-Bird Rights. This means that the highest starting salary the Celtics could offer him using the Non-Bird Exception is $3.2 million. This should be enough to retain Teague, since he settled for the minimum of $2.6 million to come to Boston. Alternatively, the Hawks could use their Mid-Level Exception or Bi-Annual Exception to re-sign Teague if he demands more than $3.2 million.
 
Other teams will have multiple ways to sign Teague as even teams without cap space could possibly use any of the Non-Taxpayer MLE, Taxpayer MLE, or possibly even the Room MLE or Bi-Annual Exception to sign him. Since he signed a minimum contract this offseason, teams will hope to get him at the minimum next summer too.