Kylian Mbappe is set for a spell on the sidelines after being diagnosed with a knee injury, which is a major blow to Real Madrid ahead of their return from the winter break. His absence will be keenly felt at Valdebebas. Since the start of the campaign, Real Madrid’s number 10 has featured in almost every fixture, scoring 27 goals across La Liga and Champions League competition.According to L'Equipe, Mbappe had been managing a knee ligament injury for several weeks, initially believing it to be a minor issue that could be played through. However, an MRI scan carried out on Wednesday morning confirmed a ligament lesion that will now require treatment and a period of rest spanning at least three weeks. The findings forced Mbappe to confront the reality that continuing was no longer sustainable, particularly after he felt increasingly restricted in his acceleration during recent matches. The warning signs had been present. Mbappe was notably left as an unused substitute during Real’s Champions League encounter with Manchester City. Despite his competitive instinct, the forward has been advised that stopping now is essential to avoid a more serious long-term issue.Real Madrid have put out a statement confirming the injury, which read: "Following tests carried out today by the Real Madrid Medical Services on our player Kylian Mbappé, he has been diagnosed with a sprain in his left knee. His progress will be monitored."The diagnosis comes only days after what should have been a celebratory high point. Mbappe marked his 27th birthday in style by scoring a late penalty to secure a 2-0 victory over Sevilla at the Santiago Bernabeu. Real had taken the lead earlier through Jude Bellingham, before Sevilla were reduced to ten men when Marcao was dismissed for a mistimed challenge on the England midfielder. With four minutes of normal time remaining, Mbappe stepped up after Juanlu Sanchez fouled Rodrygo inside the area, calmly sending goalkeeper Odysseas Vlachodimos the wrong way from the spot. It was Mbappe’s 59th club goal of the calendar year, drawing him level with Cristiano Ronaldo’s legendary tally from 2013; a benchmark long considered untouchable at Madrid.He celebrated by mimicking Ronaldo’s iconic ‘Siu’ pose. Speaking afterwards in quotes carried by Mundo Deportivo, the Frenchman was effusive in his praise for the man he has long described as his childhood hero.Mbappe said: "It's incredible, in my first [full] year to be able to do what Cristiano did. [He’s] my idol, the best player in Real Madrid's history. The celebration is for him. I wanted to give him a shout-out because he's always been good to me, he's helped me adapt to Madrid, and now it's great to help Madrid win games. Today I wanted to share that with him. I have a very good relationship with him, he’s my friend now, and I send my best wishes to him and all Madrid fans, and a Merry Christmas and a Happy New Year. It's a special day because it's [also] my birthday. I’ve always said since I was little that it's a dream to play a professional match on my birthday, and even more so for my dream team. The goal was to finish the year with a win."Looking for smarter football bets? Get expert previews, data-driven predictions & winning insights with GOAL Tips on Telegram. Join our growing community now!The injury now rules Mbappe out of Real’s first competitive outing of 2026, away to Real Betis on Sunday. More damaging still is his absence from the Supercopa de Espana, which will be staged in the Middle East. For head coach Xabi Alonso, the Supercopa represented an early opportunity to claim his first trophy in the Real Madrid dugout. Instead, he must plan without his marquee forward as Los Blancos face city rivals Atletico Madrid in the semi-finals, with a potential final against Barcelona also looming. Mbappe is also expected to miss the La Liga clash with Levante on January 17, further complicating Madrid’s domestic schedule.Add GOAL.com as a preferred source on Google to see more of our reportingThe hope within the club is that the enforced rest will be relatively short-term. If his recovery proceeds as planned, Mbappe could return to action on January 20, when Real host AS Monaco in the Champions League at the Bernabeu, a meeting rich in narrative given the forward’s formative years at the Ligue 1 side. Medical staff are determined to err on the side of caution, conscious that Mbappe’s explosive style places enormous strain on his lower body. The priority is ensuring he returns fully fit rather than risking recurrence in the business end of the season.