Both Los Angeles players have returned to training after missing the last three matches. Keane has been out with a left ankle injury and Dunivant a left leg strain.
Keane has become the captain for the Galaxy (4-3-2) this season and has taken on a bigger leadership role since David Beckham departed.
"It's frustrating because I love playing," Keane told the Galaxy's official website. "I'm not one of these players who like to be sitting in the treatment room or in the gym, I like to be out playing with the balls so it's been frustrating, but luckily enough it hasn't been a bad injury."
Dunivant has been replaced at left back by Greg Cochrane, who took his share of the blame for some miscues in Saturday's 3-1 loss at Vancouver.
Cochrane grew up in Holland, Pennsylvania - less than an hour away from Philadelphia. The rookie second-round pick said he's thrilled to return close to home.
"I'm always excited to come back here and play in front of all my friends and family, especially since I haven't been back here since the draft," Cochrane said.
Philadelphia (4-3-3) won 1-0 at Chicago on Saturday without Williams, who played every minute of every game before being sent off in the 85th minute of a 2-2 draw with Seattle on May 4.
The Union were already without center back Jeff Parke, who has a hamstring strain. Coach John Hackworth's club is in the midst of three games in eight days.
"We'll have to mix it up because we have LA on Wednesday night," Hackworth told the Union's official website. "We have a lot of depth on our roster, so I am sure we are going to have to go into it deep."
One player Hackworth will want to use is Jack McInerney, who scored his league-leading seventh goal in the 75th minute against the Fire. The 20-year-old forward, already one goal shy of his 2012 total, has scored four times in the 75th minute or later.
"He's an excellent goal scorer," Hackworth said. "He's developing, and we saw last year that he was capable of this kind of season."
Los Angeles will look to fix the defensive lapses that have been a part of its back-to-back defeats. One issue has been that the Galaxy rank last in MLS with 99 fouls committed.
Yet they still want to be more physical.
"You want to set a tone early that we're not going to be pushed around yet being smart," defender A.J. DeLaGarza said.
The Galaxy are 3-1-1 against the Union.
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- Los Angeles Galaxy
- Philadelphia Union
- Todd Dunivant