Santos took an ear but goals from Jackson Martinez and Franco Arizala in the dying minutes of the game gave Jaguares hope for the second leg.
The penchant for late goals in Mexico's Apertura playoffs continued into Sunday's showdown between Santos Laguna and Jagaures de Chiapas.
Santos took a two-goal lead in the first half through Felipe Baloy and Oribe Peralta, but goals from Jackson Martinez and Franco Arizala in the dying minutes of the 2-2 draw gave Jaguares a glimmer of hope heading into next week's return leg in Torreon.
Both teams were missing important defenders through suspension, as Miguel Angel Martinez missed out for the home side along with Santiago Hoyos for the visitors. Jaguares were able to welcome back Chilean stopper Ismael Fuentes and lined up in a 4-4-2, with Franco Arizala starting on the bench and Jackson Martinez partnering Luis Gabriel Rey up top.
Santos applied the pressure early and the visitors were duly rewarded with a goal within four minutes. Daniel Ludueña delivered a free kick into the area and Peralta and Christian Suarez both got touches before defender Baloy found himself on hand to tuck away the loose ball.
The goal put Jaguares on the back foot in front of their own crowd as Santos continued to test the home defense, though without any result. Edgar Andrade saw a good deal of time on the ball for Jaguares on the other end, but was unable to put Oswaldo Sanchez's goal under threat.
Santos' continued pushes forward were eventually rewarded just after the hour mark as Darwin Quintero fired off a shot which Jaguares goalkeeper Edgar Hernandez couldn't gather cleanly. The Apertura's leading scorer, Peralta, was on on hand to put away the rebound and give Santos a huge advantage early in the series.
Jaguares finally started to put some sustained pressure on Santos' back line after the second goal, but the visiting side defended expertly, dealing especially well with Jaguares' set pieces and balls into the area.
The home side came out of the break more focused and Andrade forced a difficult save out of Sanchez in the 53rd minute, but Santos continued to play excellent defense despite a series of balls played into the box.
As the half went on the game took a more physical tone and a series of fouls in midfield slowed down the pace of play. The physicality soon boiled over though, as Santos' Jose Maria Cardenas saw a red card for a hard challenge on Franco Arizala, forcing his team to play with 10 men for the final 19 minutes of the game.
Jagaures finally made their man advantage pay in the 84th minute as Daniel Hernandez played a precise cross into Jackson Martinez, who got everything on his header to finally beat Sanchez.
All the momentum pointed in the direction of Jaguares and they finally found the late equalizer two minutes into stoppage time. Santos' defense couldn't clear its lines, and Arizala found himself with the time and space to blast the ball home.
The two sides meet again in a week at Santos' home stadium, with Jaguares needing a win, as Santos holds the tiebreaker in the series thanks to a superior record in the regular season.