Jack (hamstring) did not practice Thursday, and he is questionable for Friday's game against the Lakers, Tim Bontemps of the New York Post reports.Jack is dealing with tightness in his hamstring, which first surfaced during Brooklyn's final game before the All-Star break. If Jack cannot play Friday night, Deron Williams will likely return to the starting lineup, with a slew of other players potentially benefiting from added minutes and/or shots.