Upon arrival, Alfred endured early struggles, but quickly gained noticed following his second season at the academy.

N'Diaye made his debut in the squad during the 2007–08 season in the Coupe de la Ligue, at the age of 17, coming on as a halftime substitute for Frédéric Biancalani in a 3–0 loss to Lens.

He was assigned the number 29 shirt and made his league debut in the opening match of the season against Lille appearing as a substitute in a 0–0 draw.

[13] On 12 January 2013, N'Diaye made his Sunderland debut at the Stadium of Light in a match which they won 3–0 against West Ham United.

[14] His full debut for Sunderland came against Wigan away, in which he produced a "wonderful" assist for Steven Fletcher to score and put them in front.

[17] On 30 January 2014, N'Diaye joined Spanish side Real Betis on loan for the remainder of the 2013–14 campaign.

[22] On 31 January 2017, N'Diaye moved on loan to Hull City for the remainder of the 2016–17 Premier League season.

[28] He played 36 games for Wolverhampton Wanderers in all competitions,[29] as he helped the club win the EFL Championship title and gain promotion to the Premier League.