Al Horford put in a game-winning type of performance as the Boston Celtics secured a 3-1 lead over the Orlando Magic with a 107-98 win on Sunday. The veteran big man recorded five blocks throughout the game. He also thrived as a screener and consistently plugged gaps on defense. 
Celtics fans have become used to Horford's Swiss Army knife approach. He excels at impacting games within the margins. He does the type of work that seldom jumps out of the stat sheet but goes miles toward winning at an elite level.
“I can't say it enough, Al is unbelievable," Jayson Tatum said during his postgame news conference. "…He’s 38 years old, and he is picking them up full court, doing whatever is asked of him. That kind of sets the tone for everybody else. He’s got the heart of a champion.”
The Celtics' focus will undoubtedly be firmly on contending for a championship. However, Brad Stevens will likely have one eye on the summer. Horford is heading toward unrestricted free agency. At 38, he's unlikely to prioritize money over situation, fit and potential success. However, he's left Boston before and can't be seen as a guarantee to re-sign.
Of course, there's also the risk that he opts to retire, which could become a genuine thought process if Boston wins another championship this season.
Still, Stevens must do whatever it takes to get Horford inked to a new deal. As we saw on Sunday, Horford is still capable of playing high-level winning basketball. When you couple that with his reported behind-the-scenes leadership and his wealth of experience, he becomes irreplaceable for the Celtics.
At least if Horford re-signs on a one- or two-year deal, Boston will have ample time to pinpoint and develop his replacement. If he were to leave this summer, the Celtics' championship window would take a serious blow.
Stevens would be wise to have a contingency in place. You know, just in case.
