 The Celtics signed forward Jason Tatum to a five-year, $314 million contract extension and guard Derek White to a four-year, $126 million extension. And the team's up for sale, so new owners have to take on those contracts. The majority ownership group of the Celtics planning to make the franchise available for sale. They announced yesterday that the managing board of the ownership group expects to sell a majority interest in the team either this year or early next year.