Aberdeen and Scotland defender Scott McKenna is likely to miss the rest of the season.
The centre-back has suffered a hamstring tendon injury which could keep him out for up to four months.
The news is a blow to the Dons' hopes of finishing third in the Ladbrokes Premiership and progressing past Celtic in the William Hill Scottish Cup semi-finals.
The injury came hours after a season-ending Achilles blow to another Scotland defender, John Souttar, ahead of the Euro 2020 play-offs this month.
Dons boss Derek McInnes said: "The result of the scan was our biggest fear. We were hoping he would be available for the semi-final.
"We anticipated him missing the next four games and the Scotland games but the news we got was the worst possible news really.
"It's more the tendon coming off the bone, which is almost exactly like Funso Ojo's one against St Johnstone. Both got a nudge in the back as they were running full pelt and I think that break in the running pattern has caused that distress on the hamstring.
"Unfortunately for us the timescale makes it very tight for him to be back playing for us this season again.
"It's not ruled out because everybody reacts differently to the rehabilitation.
"But that type of injury would normally keep you out for the best part of three to four months."
Ojo missed exactly three months, which would take McKenna almost up to the scheduled start of Euro 2020.
The 23-year-old could also be approaching a major point in his career – he handed in a transfer request in August last year after previously being the subject of bids from the likes of Hull, Aston Villa, Celtic, QPR and Nottingham Forest.
McInnes said: "Scott has been a good healer in the past so you never know but it is a real blow for him particularly in terms of his aspirations wanting to finish the season strongly, his performances have been good, and missing out on Scotland as well.
"But, selfishly, for us as well, losing such a key player."
McInnes, whose team travel to Kilmarnock on Wednesday, added: "We just need to deal with it. It's been a season with significant injuries to key players for periods of time.
"But the season is too important for us. We want to get into Europe, we want to get that third spot, we want to get another Scottish Cup final. We have to deal with it. We have to do it without Scott's help, which makes it that bit tougher for us."
Mikey Devlin came off the bench for McKenna during Saturday's cup win over St Mirren and is set to play alongside Ash Taylor at Rugby Park.
"A club like Aberdeen should have four good centre-backs," McInnes said.
"Obviously Andy Considine is filling in at left-back at the minute. Greg Leigh, we probably won't get him back until the next international break, but he is on his way back.
"The next four games we are a bit stretched in terms of defensive numbers.
"But having someone like Mikey and Ash with that experience and ability is great for us and at these times it's much-needed."
