[3] Grenier later drew interest from Lyon, whose scouts informed the youngster to continue his great play in order to join the club at a later date.

[5][6][7][8] Despite the interest, Grenier along with fellow youth player Yannis Tafer, signed his first professional contract on 15 May 2008, agreeing to a three-year deal.

[10] He also played in the 2008–09 edition of the Coupe Gambardella appearing in seven matches and scoring three goals as the squad reach the semi-finals.

[12] On 26 September, he made his senior debut in a 2–1 league win against Toulouse, appearing as a substitute for Bafétimbi Gomis.

[13] On 10 April 2012, during the semi-final of the Coupe de France against Gazélec Ajaccio, he scored his first goal with the professional team (4–0).

[citation needed] Amid interest by Arsenal over his availability for transfer, Grenier extended his contract by a further two years on 11 June 2013.

[14][15] On 29 January 2014, it was widely reported that Premier League club Newcastle United had made a 'substantial' bid for Grenier.

On the last matchday of the season, his free kick set Bakary Koné up for the only goal in the game against Nice to help Lyon qualify for the Europa League.

[citation needed] On 21 August 2014, Grenier made his first appearance of the 2014–15 season coming on as a 76th-minute substitute in the Europa League play-off match against Astra Giurgiu but left the pitch with the same groin injury that ruled him out of the latter part of the previous season and the 2014 World Cup at the final whistle.

Returning to Lyon to pass additional examinations, he learns that it suffers from a total rupture of the quadriceps of the left leg.

[citation needed] On 28 January 2017, he joined Serie A side Roma on loan until the end of the 2016–17 season with an option for a permanent move.

On 7 February 2017, Grenier made his debut for the Giallorossi in a 4–0 Serie A home win over Fiorentina, appearing as a substitute for Radja Nainggolan in the 89th minute.

[22] On 31 January 2018, Grenier signed a year and a half contract with fellow Ligue 1 side En Avant de Guingamp.

[25] On 3 March 2022, Grenier signed a contract with La Liga side Mallorca until the end of the season.

[27] On 1 September 2023, hours after leaving Mallorca, Grenier signed a one-year deal with Racing de Santander in the second division.

[32] Grenier scored a hat-trick in the team's 6–0 thrashing of Albania in the first qualifying round of the 2008 UEFA European Under-17 Championship.

[citation needed] For under-19 duty, Grenier was called up by coach Francis Smerecki, making his first appearance with the team at the 2009 edition of the Sendaï Cup.

[citation needed] Grenier received his first senior call-up by Didier Deschamps as a replacement for the injured Samir Nasri in May 2013.