By winning on a goal by Edgar Benitez, Pachuca (12 points) took over first place in the group, and left the Dynamo (seven points) needing a victory in its final game against Isidro Metapan and some help to edge out Arabe Unido (10 points) of Panama for second place.
Pachuca stunned Houston with a goal midway through the first half following a period of Dynamo control. Juan Carlos Rojas floated up the right wing and lofted a cross that dropped between Mullan and Boswell, and Benitez chested it down to smack a shot past Onstad.
Before and after the goal, Houston peppered Calero and the Pachuca net without success. Brian Mullan forced an excellent save with a low shot, and belted a first-time effort that skipped past Calero but rebounded back off the post. A shot from distance by Ricardo Clark forced another save.
Houston's disappointment and frustration persisted throughout the second half, for which U.S. international Jose Francisco Torres came on as a substitute and supplied a few classy touches. Dominic Oduro rose to meet a cross but somehow headed well wide from just a few yards away. Calero's defenders came to his rescue 15 minutes into the second half, when first Corey Ashe and then Brian Ching got shots on frame but defenders deflected both of them.
Of the four cautions issued to Pachuca players, time-wasting accounted for three of them, and it used other delaying tactics - players receiving treatment on the field, substitutions conducted at a glacial pace - to eat up time. Referee Roberto Moreno would add 3 ½ minutes of stoppage time but this seemed to be one of those nights when one of the teams would never score.
Clark headed just wide in the 88 th minute on a swerving free kick served by Stuart Holden into the goalmouth, and in stoppage time substitute Cam Weaver got his head to a cross but directed it straight to Calero. Houston finished with a 12-4 edge in shots, and took eight corner kicks to Pachuca's one to no avail, and the loss takes the Dynamo's fate out of its control.
Pachuca's win clinches it a spot in the quarterfinals. On the final day of play, Oct. 21, it hosts Arabe Unido, which won the first meeting, 4-1, and will advance by winning again or tying. Only if it loses and Houston beats pointless Metapan, can the Dynamo progress on the head-to-head tiebreaker, as both teams would finish with 10 points.
Concacaf Champions' League, Group A
Sept. 30 in Houston
Houston 0, Pachuca 1.
Goal: Benitez (Rojas) 23.
Houston - Onstad; Hainault, Boswell, Cameron, Davis (Robinson, 71), Holden, Clark, Barrett (Ashe, 46), Mullan, Ching (Weaver, 68), Oduro.
Pachuca - Calero; Lopez, Manso (Torres, 52), Caballero (Correa, 68), Rodriguez, Montes, Martinez, Munoz, Rojas, Benitez, (Gimenez, 59) Mendivil.
Referee: Roberto Moreno.