Sunderland hoping to make former Millwall forward their first summer signing

The 26-year-old will become the club's first summer signing and will strengthen Phil Parkinson's options in attack.

The versatile forward can play anywhere across the front line as has been a popular figure at The Den, where he scored 44 goals in 226 appearances over a ten-year period.

He was released following the expiration of his contract a week ago and Sunderland have moved quickly.

O'Brien scored four goals in 21 appearances across all competitions last season, operating primarily as a left winger.

He also scored 23 goals in two League One campaigns as Millwall fought their way back to the Championship in the 2016/17 campaign.

It is set to be a busy period of recruitment for Sunderland ahead of the new season, which is scheduled to begin on September 12th.

O'Brien also has four caps, and one goal, for the Republic of Ireland.