ARSENAL have been dealt a major injury blow with Gabriel Jesus out for months with an ACL injury.
The Brazilian striker had only recently returned to Mikel Arteta's starting XI.
Jesus, 27, netted three goals in Arsenal's previous four games before starting the FA Cup defeat to Manchester United on Sunday.
But his FA Cup adventure was cut short following a collision with Bruno Fernandes.
Jesus collapsed in a heap before writhing on the ground in pain.
He then received lengthy treatment from medics before being stretchered off the field.
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And Arsenal have confirmed Jesus is now facing a long time on the sidelines after suffering an injury to the ACL in his left knee.
The club have said he will undergo surgery in the coming days with the striker all-but guaranteed to miss the remainder of the season.
Arteta previously admitted: "We know more now. Not looking good at all.
"We need one more specialist and we will have more information this afternoon. I don’t want to confirm anything until the final report. It is the doctor’s job.
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"We were very worried at the time and we are very worried today."
With Jesus set for an extended period away from the pitch, Arsenal could be forced to dip into the January transfer market.
The Gunners could explore a potential loan deal for a striker, but they will not be able to sign anyone from the Premier League due to their two allocated slots being taken up by Raheem Sterling and Neto.
Instead, they will have to look abroad.
Arteta and Co may reignite their interest in Juventus striker Dusan Vlahovic before the window closes.
Arsenal pushed to sign him three years ago but lost out to Juve just before the January deadline.
However, the Serie A giants could be open to letting him go this month.
They reportedly offered him to Manchester United as part of a swap deal for Joshua Zirkzee last week.
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Discussing the possibility of signing another forward this month, Arteta added: "We are actively looking in the market, the same since day one. We would be naïve not to do that.
"We are trying and let’s see what we are able to do."
Arsenal ratings vs Man Utd as Martinelli looks lively but wasteful Havertz costs Gunners another trophy chance
KAI HAVERTZ missed two sitters and a penalty in the shoot-out as Arsenal were dumped out of the FA Cup.
The Gunners huffed and puffed but failed to find a winner, even after extra-time, against Manchester United’s 10 men.
And it all went wrong in the penalty shootout as Altay Bayindir saved Havertz’s effort.
Here is how SunSport's Kealan Hughes rated the Arsenal stars...
DAVID RAYA - 6
Could do nothing about United's goal and produced a stellar stop to deny Zirkzee in extra-time.
JURRIEN TIMBER - 7
Very effective on the overlap and worked well being fed by Odegaard.
Tested a couple of times by Alejandro Garnacho who proved a problem on the counter-attack.
WILLIAM SALIBA - 7
Dealt with Hojlund well although the striker did not pose much of a threat.
GABRIEL - 6
Terrible error to lose possession to Alejandro Garnacho who was put through on goal and set up Bruno Fernandes to score.
Made amends with a brilliant finish Bukayo Saka would have been proud of.
MYLES LEWIS-SKELLY - 5
A quiet game at left-back, probably should have got forward more particularly after United went down to ten men and had Garnacho filling in at right-back.
JORGINHO - 5
Kept things ticking over in the middle and was always an outlet for his team-mates.
MIKEL MERINO - 4
Anonymous in the middle. Difficult to see what he brings to this Arsenal side.
Missed a good chance to put his side ahead moments after the equaliser and was taken off shortly after that.
MARTIN ODEGAARD - 7
A pleasure to watch. Made everything happen, his ability to turn on the ball in the middle of the park created opportunities time after time.
But he missed the chance to win the game from the penalty spot.
GABRIEL JESUS - 6
Lovely pass to break the lines and put through Martinelli, who found the back of the net but was offside.
Fell awkwardly when defending a cross in the first half and was carried off on a stretcher.
GABRIEL MARTINELLI - 7
Was the main attacking threat in the first half with his direct style causing the visitors all sorts of problems.
Produced good movement and a finish to match but his goal was disallowed for offside.
KAI HAVERTZ - 3
Won the penalty after a deft touch past Maguire.
But he missed two sitters including one just three minutes from time to win the match, and his penalty miss proved decisive in the shoot-out.
SUBSTITUTES
Raheem Sterling (for Jesus, 40mins) - 6
Looked sharp when he got the ball and did well in the build-up to Havertz winning the penalty.
Declan Rice (for Merino, 73mins) - 6
Almost scored with what might have been his first touch but his header was brilliantly saved.
Should have grabbed the winner in the dying moments but his low effort was again superbly matched by Bayindir.
Leandro Trossard (for Lewis-Skelly, extra-time) - 5
Will wonder how he didn't score after Matthijs de Ligt produced a goalline clearance to deny him.
Blazed over with an effort from just outside the box.
Thomas Partey (for Timber, 101mins) - 5
Put in a few good crosses. Came close to a winner with an effort that was deflected narrowly over the bar.
Kieran Tierney (for Jorginho, 113mins) -
His arrival onto the pitch was greeted with a big cheer but he did not have much time to impact the match.