Gio Savarese suggested the Portland Timbers may have to look at options in the transfer market after Ismaila Jome sustained a season-ending Achilles injury.
Jome had made three substitute appearances for Portland before rupturing his left Achilles tendon in training on Monday.
The left-back had been brought in primarily as back-up for Claudio Bravo, and his loss is a big blow for the Timbers.
Ahead of Saturday's meeting with Houston Dynamo, Savarese said: "A tough one. It is a type of injury that will take a while for him to come back.
"We all feel very bad about this situation. He was very excited to be part of this group and this is a difficult moment for him, for all of us and it's unfortunate that it happened.
"It becomes a bit more difficult because he was the replacement left-back and also gave us some very good things going forward. Now we have to make sure that we adapt with the players that we have, we will continue to work with them to make sure they could potentially play in that position.
"We'll also probably go out there and try to find one more player that could play center-back or left-back or concentrate on a left-back who can come in."
While Portland started their season with a defeat to Vancouver Whitecaps, Houston - who endured a difficult 2020 - beat San Jose Earthquakes in their opener.
"We understand that last year wasn't our best year," defender Zarek Valentin said.
"Let's just call what it is right, we finished last in the West. We think that there were a lot of great moments, but ultimately, we didn't get the job done.
"There is a lot of motivation this year and I don't think there's a lot of belief in the MLS world. Ultimately, we believe in ourselves. That's what matters most."
PLAYERS TO WATCH
Portland Timbers - Diego Valeri
Diego Valeri has been involved in 105 goals at Providence Park since debuting for the Timbers in 2013 (51 goals, 54 assists).
Houston Dynamo - Maximiliano Urruti
Former Timbers striker Maximiliano Urruti scored on his Dynamo debut against San Jose in the season opener. It was the second time Urruti scored on his team debut in MLS (also with FC Dallas in 2016).
KEY OPTA FACTS
•The only other player with more than 77 goal contributions in home matches since Valeri made his Timbers debut is Bradley Wright-Phillips (91 - 74 goals, 17 assists).
•The Dynamo extended their season opening unbeaten run to 10 games (W7 D3) with a victory over San Jose. Houston have opened the season with two straight wins three times before: in 2012, 2014 and 2017.
•The Timbers are unbeaten in their last seven home regular season matches against Houston (W6 D1) after losing their first-ever home MLS match against the Dynamo in 2011.
•Houston, however, have recorded a playoff win at Providence Park in that time, winning 2-1 in 2017.
•Portland's 1-0 defeat to Vancouver marked the third time the Timbers have lost their season opener in the last four years (D1). It was only the second time Portland failed to score in their first match of a season (2015 vs. Real Salt Lake) as they've never gone two matches into a season without finding the net.