“Injury time” has taken on new meaning for the bruised and battered Earthquakes, who are almost defenseless for their Champions League quarterfinal game Wednesday night against elite Mexican club Toluca FC.

The Caribbean, Central American and North American regional tournament showdown would have been challenging in the best of circumstances. But the Quakes landed in Toluca this week with no good options on defense.

An already depleted backline took an untimely hit last weekend when reserve center back Jason Hernandez suffered a left thigh muscle strain in the Major League Soccer season opener. He was starting in place of U.S. national team defender Clarence Goodson, who is out with a calf muscle strain.

Also out: fullbacks Brandon Barklage (hip flexor), Andreas Gorlitz (hamstring) and Jordan Stewart (hamstring) and center back Victor Bernardez, who is suspended for the CONCACAF match because of yellow cards.

The only healthy center back is 6-foot-2 rookie Joe Sofia of UCLA, who saw limited action in the preseason. Ty Harden also could play central defender, although he has yet to fully recover from season-ending hip surgery last year.

The frustrating situation led coach Mark Watson and his assistants to hole up in the locker room for more than an hour after the Earthquakes rallied for a 3-3 tie against Real Salt Lake in the MLS opener at Buck Shaw Stadium. San Jose’s brain trust wasted little time in trying to figure out what to do against formidable Toluca, as strong at home as the Quakes are at Buck Shaw.

The Diablos Rojos are unbeaten in their past 12 Liga MX games at Estadio Nemesio Díez Riega. They have a big advantage against San Jose because the subtropical region outside of Mexico City sits at 8,700 feet.

Watson might need to abandon the team’s traditional 4-4-2 formation, particularly considering away goals are tiebreakers for the CONCACAF tournament.

The teams tied 1-1 in the opening leg of the home-and-home series last week in Santa Clara. The Quakes need a victory, a draw with at least two goals or a 1-1 tie followed by a penalty-kick shootout advantage to advance.

The Earthquakes might try a 3-5-2 format because of the lack of center backs and the need to score away goals.

“Sometimes three in the back has been effective in getting goals,” general manager John Doyle said.

Whatever formation they use, the Quakes will play aggressively.

“We’ll take whoever is healthy and go after them,” goalkeeper Jon Busch said. “We’re always up for challenges, and this is just another challenge.”

It’s a big one as Toluca is 8-1-2 in Mexico’s top division, second to Cruz Azul of Mexico City.

In an emergency measure, Watson started Cordell Cato and Shaun Francis as fullbacks against Real Salt Lake. Neither was projected as a major contributor on defense this year, and once the team returns to full strength it’s doubtful to see them paired on the backline.

“We kind of threw things together,” Watson said.

Barklage was a late-scratch after aggravating the hip during a practice drill Friday.

Watson said Barklage might be available when the team plays at Sporting Kansas City on Saturday. Goodson also could return by the weekend. And Stewart is not expected to miss too much time, either.

Cato, a natural right-side midfielder, didn’t mind switching positions because he just wants to play. Cato needs to diversify to remain on the field since the signing of midfielder Yannick Djalo of Portuguese club Benfica.

“It’s just something to get used to,” he said of playing defense.

Cato probably will get another chance to get comfortable on the backline Wednesday. Because when it comes to Toluca, the Earthquakes will have to make do with what they’ve got.

Contact Elliott Almond at 408-920-5865 and follow him on Twitter at Twitter.com/elliottalmond.