Yalcouye was shown a straight red card in the 34th minute of the 1-0 loss after he appeared to clash head-to-head with QPR defender Steve Cook.
The 19-year-old Brighton loan player squared up to Cook - forehead-to-forehead - after a penalty decision had not gone in Yalcouye’s favour before the 34-year-old former Bournemouth defender fell backwards.
Swansea were already trailing to an early goal from Rumarn Burrell by that stage and although they rallied with 10-men for the final hour, they lacked the firepower to claim an equaliser.
“He's devastated in there,” said Sheehan of the young Ivorian midfielder.
"Obviously we suffered from that. It changes the game. It makes it an uphill battle. I think you see a young 19 year-old lad up against a very very experienced player and I think that's the way it happened."
"Obviously, Steve Cook and Malik came together, he’s been enticed, and he went down like he got hit by an absolute truck.
"I haven't seen the incident totally, but I don't think he's headbutted, but I think both players at different instances have stuck their heads together and probably whoever has that momentum.
"But the reaction of jumping back. That's an experienced player or doing what has to be done, really, and we've suffered from that tonight.
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“But look, Malik is a young player. We have him on loan from Brighton and he's a talent and we've suffered from that tonight, but I'm not going to throw anybody under the bus or anything.
"This is just a learning curve and he'll get better for it.
"I'll have a one-to-one with Malik about and speak. But this is an incident that happened very quickly in the heat of the moment, so it's disappointing that it happened, but that's the way it is."
The defeat means Swansea have only won once in their last seven league matches and have dropped to 16th in the table.
They can point to Yalcouye’s naivety - or Cook’s streetwise cunning - but the fact is Swansea were at their most ineffective in the opening half an hour when the young Ivorian was still on the field.
Their approach play was one-paced and predictable, their passing was sloppy, and their marking was poor - in particular when QPR’s Isaac Hayden was allowed to run in behind before crossing for Burrell’s only goal of the game.
Sheehan’s side were actually much better at the start of the second-half, when they managed to inject some urgency into their play with only 10 men.
Swansea City head coach Alan Sheehan. Pic: Alamy
But when the chances finally came, substitutes Zan Vipotnik and Melker Widell were unable to seize their opportunities.
It’s hardly a crisis - yet - at Swansea, but things appear to be trending in the wrong direction after a summer transfer window that appeared to have laid a foundation for progress.
Among a number of alarming statistics, perhaps the most worrying is that Sheehan’s team have not won at home in the Championship since August 16 when they beat Sheffield United, 1-0.
Since then, they have failed to put away Watford, Hull City, Millwall, Leicester and now QPR, with three defeats following the initial two draws.
Sheehan still has plenty of credit in the bank from his shrewd guidance of the squad last season and there was no shortage of application when they went down to 10 men.
But the lack of quality in the final third is proving a problem at present and if Swansea struggle to beat out-of-sorts Norwich City at home on Saturday then the situation will feel more acute.
Sheehan admitted: “We didn't start the game well. You don't get time to wake up in the Championship.
“They scored with one of their first opportunities, then I think we reacted, woke up a bit and then obviously the sending off happens and it's an uphill battle.
“But we regrouped at half-time and made a few changes and I think there's a lot of positives to take out of that second half in terms of playing for 60 minutes with 10 men and having opportunities near the end to salvage something.
“That was the game-plan because if you concede the second and third early in the second half, it can be quite difficult.
“I think that effort and honesty from the players out there - I think I think they're the positives to take them tonight.”
Queens Park Ranger manager Julien Stephan insisted: “I am very happy with the win and especially how we managed to control the second half without the ball.
“It was not perfect because it would be perfect if we scored the second or third goal.
"It's just a question of efficiency - to kill the opponent - and we didn't do that.
“It's a good win for us. But in this kind of game you never know at the end what can happen when you stay at 1-0 the last five minutes.”
On the red card for Swansea’s Malick Yalcouye he added: “To be honest, I didn't see the situation exactly. But if the referee took this decision, I think it's a good decision.”
Burrell gave Rangers a deserved 18th minute 1-0 lead when he latched onto Isaac Hayden’s chipped cross to clip a volley past Vigouroux.
Swansea had failed to track Hayden’s run and basic errors elsewhere meant they carried few threats of their own in the early stages.
They were just starting to press with more cohesion around the half hour mark when Yalcouye was shown his straight red.
QPR held their lead until the break, but came under more pressure from 10-man Swansea at the start of the second-half.
A header from Marko Stamenic went over the bar before Nardi had to make a brave dive in his goalmouth to clear a teasing cross from Josh Tymon.
QPR substitute Ilias Chair had a chance to make the game safe for his side in the 78th minute when he was sprung beyond Swansea’s defence, but was denied by Vigouroux.
Jimmy Dunne then came close to making it 2-0 when he finished a surging run by striking the post before Jonathan Varane put the rebound wide.
