The Impact (10-13-3) are riding a season-high three-game winning streak and are coming off only their second away victory of the season at New England.
The Major League Soccer expansion side has won four of the last five, and are in position to take a shot at making the playoffs if they can stay hot over their final eight games of the regular season.
A win against San Jose (14-5-5) would be a confidence booster, although Marsch knows it won't be easy. The Earthquakes are coming off a rousing victory of their own, a 2-1 result against Seattle on a late goal from forward Steven Lenhart.
"You have to marvel watching them play because you can see the belief they have that no matter what the situation, they're going to push at the end of the game and get a result somehow," Marsch said this week. "It's a game that's going to require us physically to be able to match their will and also for us to do well in certain critical moments the box.
"They're good at set pieces. At the same time, we still have to play our game. At home we've been quite good and we know we can still manage to put things on our terms."
The Impact are expected to be without former Italian league star Alessandro Nesta, who has taken charge of the defence since joining the club a month ago, due to a right knee sprain.
With his central defence partner Nelson Rivas serving the second of a two-game suspension for head-butting an opponent, it leaves the Impact vulnerable in a key area against one of the league's most dangerous attacking clubs.
However, they have depth in veteran Matteo Ferrari, Shavar Thomas and Hassoun Camara, who has been playing right back since Nesta's arrival.
Especially dangerous is Earhquakes striker Chris Wondolowski, who leads MLS with 17 goals in 18 games, although he hasn't scored in four games since missing a penalty shot against Dallas.
"I really like Chris," said Marsch. "He's a good guy.
"He's paid his dues over the years. From the soccer side, it's a big challenge for us. He's so clever and smart. He only needs a little window to make plays and he seems to be able to do it every game. He'll certainly be a focus of what we're going to do on Saturday."
Goalkeeper Troy Perkins will be looking to make it two wins in a row since he was acquired last week from the Portland Timbers for Donovan Ricketts. He knows Wondolowski well from playing in the Western Conference.
"The best way to stop him is to deny him service," said Perkins, whose stop last week against New England's Saer Sene was voted save of the week.. "If we can close down service from the flanks, he'll go searching for balls. That's what we want. Their other guys up front are also dangerous."
San Jose will likely be paying attention to Montreal striker Sanna Nyassi. His goal on a run up the middle and blast to the top corner in a 1-0 win over New England was voted MLS goal of the week on the league's website.
Nyassi has been used mainly off the bench recently, but has been scoring big goals late in games.
"He's an explosive player, and he's shown the ability to make explosive plays all year," said Marsch. "It was a spectacular goal and it came at a good moment.
"He's really moved himself along in terms of his intelligence on the field and his understanding of what we want from him. He works so hard. I'm happy for him now that he's scoring goals and showing good form."
Some have taken to called Nyassi a super-sub, but Marsch says he brings more to the squad than that.
"That's his role on some days, but we also felt that when he started he's done well," the coach said. "It's not like that's the only way we think of him."
The Impact are just out of playoff position in sixth place in the East, three points behind D.C. United, who have four games in hand.