Chelsea officially announces the appointment of a 41-year-old young coach, the "most unknown" manager in the club’s Premier League era has arrived.

Written by Han Bing On January 6, Strasbourg’s Ligue 1 head coach Rosénier held a farewell press conference, followed by Chelsea’s announcement of the 41-year-old English coach’s appointment. Rosénier, of Sierra Leonean descent, becomes Chelsea’s second black head coach in history after Gullit (1996), and the second domestic black head coach in the Premier League after Paul Ince (2008, Blackburn).

Promoted from a Ligue 1 satellite club, Chelsea’s choice of coach this time is unprecedentedly hasty. Strasbourg was reluctant to lose their coach mid-season but had no choice as a "subsidiary." Both British media and Chelsea fans are unfamiliar with Rosénier; some even label him as the "most unknown" coach in Chelsea’s Premier League history. Previously, Chelsea’s head coaches either had distinguished playing careers or successful coaching records. Rosénier’s playing career was unremarkable, and his best coaching achievement was leading Strasbourg to 7th place in Ligue 1.

In Chelsea’s Premier League era, the first coach Porterfield was a Sunderland legend as a player; subsequent coaches like Hoddle, Gullit, Vialli, Di Matteo, Lampard, and Maresca all had notable playing careers. Renowned coaches such as Ranieri, Mourinho, Scolari, Ancelotti, Conte, Sarri, and Tuchel have also led the team. The young Villas-Boas was brought in by Abramovich for a world-record €15 million compensation fee after winning three trophies including the Europa League, Primeira Liga, and Portuguese Cup.

One of the few exceptions is Potter, who had no trophies as a player or coach but had three Premier League seasons before joining Chelsea, leading Brighton to their highest-ever 6th place finish in the top flight. In September 2022, Chelsea spent £16 million (€18.5 million) plus £6.5 million (€7.5 million), totaling €25 million to bring Potter and his entire coaching staff, setting another world record. Even Rosénier’s predecessor Maresca cost Chelsea £9.2 million (€10 million) in 2024.

This time Rosénier was "promoted," and although Chelsea expressed willingness to pay compensation, the amount is expected to be minimal.

Rosénier is a "data-driven" young coach with a refined image, and his performance in Ligue 1 has been fairly good. Last season, he led Strasbourg—the youngest team in Ligue 1—to 7th place, briefly reaching as high as 4th near the end of the season. This season, Strasbourg has remained stable within the top 8, even reaching 3rd place at one point.

Tactically, Rosénier favors a three-defender system and is skilled at switching between three and four defenders, so taking over Chelsea mid-season won’t require a major tactical adjustment period. Most importantly, he is familiar with Chelsea’s three directors: he knew Winstanley as a player, was a colleague of Stewart’s, and worked alongside Jewell when coaching at Brighton’s academy. Communication with Chelsea’s "director group" is smooth, and he is the "compliant" coach favored by the American owners.

Another advantage of Rosénier is that he grew up in England, gaining local experience both as a player and coach. He has six seasons of coaching experience in England, starting in 2018/19 with Brighton’s reserves, later assisting Cocu and Rooney at Derby County, and serving nearly two seasons as head coach at Hull City. He credits Rooney for teaching him a "winner’s mindset," and when Cocu was sacked in November 2020, British media widely considered Rosénier, then assistant coach, more qualified to be head coach—since he largely led daily training and tactical setups.

It’s worth noting that several coaches Rosénier faced during his time "leveling up" in the Championship are now in the Premier League, including Frank (Tottenham), Eddie Howe (Newcastle), Marco Silva (Fulham), and Parker (Burnley). Notably, in the 2023/24 season, he also competed against Chelsea’s former coach Maresca in the Championship, remaining unbeaten with one win and one draw.

On January 7, Rosénier will watch Chelsea’s match against Fulham live, missing the chance to face his old Championship acquaintance Marco Silva. He will start training with the team on January 8, with his debut on January 10 in the FA Cup away game against Charlton. Charlton’s head coach Nathan Jones was a predecessor of Rosénier’s in Brighton’s coaching staff. Although they were familiar in the Championship, Jones previously coached Luton and Charlton, so they never met directly. Now they finally have the opportunity to compete. For Rosénier, under great pressure to lead a top club for the first time, this represents a familiar and relatively relaxed beginning.