When the Portland Timbers inked Roy Miller to a contract in January, the signing was met with little fanfare and a whole lot of skepticism.

Miller had spent six solid seasons as a reliable defender for the New York Red Bulls before going on to anchor the backline for Costa Rican powerhouse Deportivo Saprissa. But Miller was best remembered by MLS fans, albeit unfairly, for a handful of glaring gaffes at left back during his time in New York. When Portland announced the signing, D.C. United even tweeted - and then deleted - a video of Miller making a critical defensive mistake while with the Red Bulls.

But the skeptics were wrong. Miller has turned out to arguably be Portland's most important acquisition of the offseason.

"I'm not sure we'd be where we're at without him," Timbers coach Caleb Porter said.

The Timbers made the decision to target Miller last December after competing against Saprissa in CONCACAF Champions League and seeing the composure, consistency and versatility that Miller brought to their opponent's backline.

Heading into the 2017 season, Portland expected Miller to provide depth primarily at center back and fill in at left back as needed. Instead, the Timbers have been forced to use Miller as a starter at both center back and left back for the majority of the season as they've dealt with an onslaught of injuries on defense. Miller has made 24 starts this year and become a reliable option for Portland on the backline.

"The adjustment hasn't been as difficult because before I came here I already knew about MLS, had played in MLS," Miller said. "I always try to be ready, whether I'm going to play left back or center back."

The Timbers had expected center backs Liam Ridgewell and Gbenga Arokoyo to anchor the backline in 2017, but Arokoyo suffered a season-ending injury in preseason and Ridgewell has made just 11 starts as he's dealt with multiple injuries as well.

With the defensive turmoil, Portland (12-10-8, 44 points) has struggled at times on the backline and has conceded a poor 47 goals in 30 games. But the Timbers, who currently sit in second place in the Western Conference standings, have managed to keep pace in the playoff race and taken steps forward on defense in recent weeks thanks in large part to the success of their depth pieces. Miller has started in each of the last five games and provided consistency on defense as the Timbers have posted a 3-1-1 record during that span.

"This year, we've had depth and because of that we're in the positon that we're in," Porter said. "These guys - Lawrence (Olum) and Roy (Miller) and (Jeff) Attinella - those signings were just as important as any of the other signings we made in the offseason."

It's unclear what role Miller will play in the final stretch of the season as the Timbers start to return to full health on defense.

Portland acquired center back Larrys Mabiala during the summer transfer window and the 29-year-old has been key on the backline in the last two months. Ridgewell, who had made just one start since June, finally returned to the starting 11 last week against Real Salt Lake. And left back Vytas, who has dealt with multiple injuries this year, is now fully healthy.

Porter rewarded Miller for his performance by starting him over Vytas at left back last week as the Timbers fell 2-1 to Salt Lake. But while Miller tied the Timbers season-high for tackles in the game with eight, he is a defensive-minded player that doesn't always provide the same offensive push that Vytas is capable of bringing from the left back position.

If the club can stay healthy, Porter will have to make a tough decision between starting Miller or Vytas moving forward.

"(Miller) brings good balance, good defending," Porter said. "He brings good air play, set pieces and he's a good passer as well. When you look at all of those things, that was the decision (in Salt Lake)."

Regardless of the role he plays in the final stretch of the year, Miller's signing has already paid dividends for Portland this season.

"I always try to do my best," Miller said. "If (Porter) needs me, whatever position he needs me at, I'll be ready."

-- Jamie Goldberg | jgoldberg@oregonian.com

503-853-3761 | @jamiebgoldberg