The Cowboys are signing defensive ends Jeremy Clark and Jimmy Saddler-McQueen to address depth at a position that has been depleted by injuries.
Spears, a first-round pick in 2005 who has started since midway through his rookie season, might have played his last down with the Cowboys when he suffered a strained calf in Sunday's 45-7 loss to the Green Bay Packers.
While Spears never developed into a dominant player like fellow 2005 first-round pick DeMarcus Ware, he had been a model of durability. Spears had never missed a game in his NFL career, a streak of 88 games that will be snapped Sunday.
Injuries to Hatcher (groin) and rookie seventh-round pick Sean Lissemore (ankle) pushed the Cowboys to sign Clark and McQueen. Hatcher is likely to be out at least a couple of more weeks after missing Sunday's game. Lissemore, who was injured Sunday, could be out four to six weeks.
Clark's NFL experience consists of four games with the New York Giants in 2008 and stints on the Atlanta and Philadelphia practice squads. He was cut by Arizona this summer. The Cowboys released Saddler-McQueen in the final cuts. He spent several weeks this season on the St. Louis practice squad.
Owusu-Ansah, a fourth-round pick who played solely on special teams this season, suffered a high ankle sprain against the Jacksonville Jaguars on Oct. 31.
Tim MacMahon covers the Cowboys for ESPNDallas.com. You can follow him on Twitter.