The Wizards are looking to beat the Spurs for the first time since November 2005.
Porter scored 11 points in 28 minutes after not playing Friday against Thunder.
Forward has logged 48 minutes in 30 games this season.
Allen is contemplating whether to return for his 19th season or retire
The rugged forward-center joins a crowded front court after finding fun in basketball again in the playoffs with the Mavericks last season.
Washington has lost 15 straight games to the Spurs, dating back to Nov. 12, 2005 - before 12 players on the Wizards' roster even entered the league.
The Spurs have had success by sharing the ball for years. The Wizards are taking a similar approach in recent wins.
San Antonio's unselfish play proves too much for Washington to overcome.
Wizards hope to avoid starting the season with 12 straight losses.