To advance out of the group stage of the CONCACAF club championship, Paul Mariner's team has to win by three goals — or score four or more and win by two.
Santos, which leads TFC by three points in the group, advances with a win or tie. It can also lose and move on if it does not give up too many goals.
Wednesday's scenario would have been different if Toronto had not given up goals in the 90th minute and stoppage time in a 3-1 loss to the Mexicans at BMO Field on Aug. 28.
Toronto, in the midst of an 0-9-4 run in league play, has gone 1-5-2 in all competitions since that Santos Laguna defeat.
A goal bonanza in Torreon, Mexico, seems unlikely for the visitors. Toronto is tied for 16th in the 19-team MLS in goals scored with 35 in 33 games. Plus big French striker Eric Hassli will miss the trip after his wife gave birth to a baby boy. So the offence will be entrusted to Jamaican international Ryan Johnson (seven goals) and rookie Luis Silva (five).
Mariner believes his team has an edge on the counter-attack and set pieces. But while Toronto needs goals and lots of them Wednesday, he says his players have to use their head.
"We can't go stupid. We can't just go all out attack ... because you can see in a split-second they can open you up."
Toronto is no stranger to the attitude of the Estadio TSM Corona in Torreon. Santos Laguna thumped them 6-2 in April in the semifinals of the 2011-12 competition, scoring four unanswered goals in the second half.
"It's a great place to go," Mariner said of the Santos home. "It's a wonderful theatre of football. It's a tremendous stadium. They're an excellent team. It presents a lot of challenges obviously. But it gives people a chance to further their career, whether it's going up the ladder or going back down the ladder."
The teams tied 1-1 in Toronto in March.
Santos has had a bumpy ride of late in the Mexican league. Beaten 4-1 on Saturday in Toluca, Santos is on a three-game winless streak and sits sixth in Mexico’s Apertura tournament with 20 points from 14 games.
But it showed its class in a 2-1 exhibition loss to Real Madrid in Las Vegas in August.
"No question about it, we're going to have to bring our A game," said midfielder Terry Dunfield. "They're one of the best teams this side of the planet probably. It's another opportunity for everyone to show what they can do."
Santos is 3-0-0 in CONCACAF Champions League play, having outscored its opposition 11-1 including a 3-1 win at BMO Field.
The Mexican side looks to American Hercules Gomez and Oribe Peralta up front.
"They're an exceptional pairing," said Mariner, a former English international forward. "Their interplay is excellent with one-twos around the box so we must be fully aware of that."
Toronto is 2-1-0 thanks to a pair of wins over El Salvador's CD Aguila which has lost all four matches and been outscored 17-1.
Only the eight group winners advance to the quarter-finals of the CONCACAF club championship, with the Los Angeles Galaxy, Seattle Sounders and two-time defending champion Monterrey having already booked their tickets to the round of eight.
Mariner, who is taking just 17 from his injury-ravaged squad to Torreon, has played the international card to his players.
"We're representing Canada," Mariner said after a wet practice Tuesday before heading to Mexico. "I said that to the players this morning. It's very important.
"We've just tweaked out system a little bit. They've got some very good players. Obviously it's going to be difficult, but like I said to the guys this morning, it's 11 blokes against 11 blokes so let's get after it."
With Irish international Darren O'Dea and Logan Emory among the injured, Mariner will look to Richard Eckersley and Adrian Cann at centre back with Aaron Maund shielding them in front.
Freddy Hall will start in goal backed up by Quillan Roberts as Milos Kocic attends to his newborn triplets at home.
Others on the injured list are Stefan Frei, Torsten Frings, Danny Koevermans, Ty Harden, Keith Makubuya and Quincy Amarikwa.
Mariner, while not begrudging Hassli his family time, noted he was "an old-school guy" when it comes to work and childbirth, having trained and played while his three kids entered the world.
"Those days are behind us now," he said. "We've got to get up to the modern era. I think it's only right that Eric stays behind with his wife."
After the Santos game, Toronto (5-20-8) wraps up league play Sunday in Columbus (14-12-7).