The Argentines each scored to lift the Timbers to a 2-0 victory over the visiting Houston Dynamo on Saturday night.
"Their relationship has been huge," Portland captain Will Johnson said. "It's gotten us quite a few points, especially the last four or five games. ... They play off each other really well."
In the last four games, all as starters, Urruti and Fernandez each has two goals and an assist.
"They're not going to (rest on their laurels), because we've got competition, and that's what we've created," Portland coach Caleb Porter said. "It's created a trust."
The Timbers opened the scoring in the 34th minute, when Urruti headed a free kick by Jorge Villafana into the upper right corner for his third goal of the season. For Villafana, it was his third assist of the season, and his second consecutive game with an assist. That makes him the first Portland defender to earn assists in consecutive games since the team joined MLS in 2011.
"Jorge's certainly gotten us a couple goals off his service, set piece-wise, and he looks really confident right now, for sure," Porter said. "It seems like the game is flowing for him."
Fernandez added his goal in the 60th minute off of a penalty kick. A Timbers corner kick landed at the feet of Rodney Wallace and while attempting a shot, referee Baldomero Toledo judged the Portland midfielder was fouled and awarded the penalty. Houston goalkeeper Tyler Deric dived the wrong way as Fernandez placed a solid shot into the upper right corner for his second goal of the season.
Houston head coach Owen Coyle was not happy with the penalty call.
"A very soft penalty," he said. "It's goals that change games, so those game-changing moments, we think people have to get them right. And my opinion, they certainly didn't go Houston Dynamo's way tonight. And that's a very polite way of saying it. I don't want to get myself in too much trouble."
The victory extended Portland's winning streak in MLS to four games, doubling the previous record coming into the season. The Timbers also won in the U.S. Open Cup on Tuesday against the Seattle Sounders.
Houston came into the game short-handed, with four starters missing. Brad Davis and Boniek Garcia are out with injuries, while Jermaine Taylor and Giles Barnes are on international duty with the Jamaican national team.
"You always want your best players available," Coyle said. "And we were without four starters, four quality players, but you can never foretell what would have happened if they had been in the team or not."