The intense Texan heat and tired legs contributed to a scoreless slugfest for the second game in BBVA Compass Stadium.
With Houston playing a second game in three days at the newly-opened BBVA Compass Stadium, Brian Ching was used as a substitute in the scoreless draw.
Despite holding nearly 60 percent of possession and doubling the Timbers' shots (18 to nine), Houston could not find an opening. Troy Perkins, wearing a face mask, pulled off seven stops.
"I just did my job," Perkins said. "At the end of the day that is all I can do. Seeing a zero on the scoreboard makes me happy and makes all the guys in front of me happy. Some nights they put them in the corner and some nights they don't."
The impressive saves came as the clock wound down, with the most telling being a one-on-one shoulder block against Calen Carr.
Minutes before that chance, Carr had almost zipped clear on goal except for a late Mamadou 'Futty' Danso tackle that took him out. Danso was the last man and clearly caught Carr but curiously avoided even a free kick.
Portland has never beaten Houston in franchise history.
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