The 25-year-old, who is currently on loan from Eintracht Frankfurt, suffered a cruciate ligament injury in their 1-0 win over the Blues – and was carried off on a stretcher during the early stages on the match.
Since Saturday’s game, scans have revealed that the Dutchman has ruptured a ligament in the same knee he damaged three years ago, causing him to be sidelined for the rest of the campaign.
On Monday evening, the Dutchman issued a statement on Twitter, stating: “While I'm typing this my eyes are full of tears. I pray before each game and I ask God to let everyone end the match healthy whether we win or lose.
“As you already may have heard, Chelsea was my last game for this season.
“I had in all fronts an incredible, beautiful, fun and especially a good half year and I want to thank everyone who was involved in that.
Willems also revealed that he believes he will play for the club again, despite his loan deal expiring at the end of the season.
“I believe in the plan I made with God and the path we have chosen” he adds. “I pledge to do everything I can, so it will not be my last game for Newcastle United!!!”
During Newcastle’s pre-match press conference for Tuesday night’s game against Everton, Magpies boss Steve Bruce also confirmed the bad news. “It's what we feared” Bruce said, as quoted by the Daily Mail. “He's ruptured his anterior cruciate and will miss, obviously, the rest of the season.
“The big thing now is just the welfare of Jetro, getting his head around that. Unfortunately, it's his second serious knee injury in three years.
“He's a strong-minded individual and really the big thing now is to let him have the operation and recover, and then we'll review the whole situation in a few weeks. It's all too raw for us at the moment to even speculate or comment on what's going to happen.”
The defender has made 20 appearances for Newcastle this season, scoring two goals and providing three assists in all competitions.