Djalo has been a key as the Earthquakes found some form to be in the hunt for a play-off place in the Western Conference.
The Portuguese attacker has scored twice and set up two other goals in the past two matches but is out for up to four weeks with a quad strain.
Earthquakes coach Mark Watson said Djalo could return earlier.
"We've heard from one to four weeks," Watson told a news conference.
"They're still in the evaluation process. It's still settling down from the weekend.
"He's very optimistic. He feels he's improved a lot just in the past couple of days but we're still working off that [one-to-four-week] timeframe. It's kind of monitoring it day to day."
A three-match unbeaten league run has seen San Jose close to within seven points of the fifth-placed Colorado Rapids.
They meet a red-hot Galaxy side, who sit third in the conference after four wins in their past five league matches.
Robbie Keane netted a brace in a 3-1 win over the Portland Timbers last time out, while the Galaxy have scored six times in their past two matches.
Toronto will be without injured striker Jermain Defoe for their trip to the Columbus Crew and FC Dallas host the Colorado Rapids.
DC United visit Real Salt Lake in a clash between teams sitting second in their respective conferences.
The Montreal Impact are out to avoid a seventh straight league loss when they visit the Philadelphia Union.
Elsewhere, struggling Chivas USA take on the Portland Timbers and East leaders Sporting Kansas City travel to the Vancouver Whitecaps.
The New York Red Bulls meet the Chicago Fire and the West-leading Seattle Sounders are looking for a return to form when they face the Houston Dynamo.
