The 34-year-old joins from FC Nordsjælland, where he most recently worked as head of set pieces and analysis, bringing extensive experience from Danish club football to the Premier League.
Sunderland confirmed the appointment on Tuesday, although Herdal must still secure the necessary visa and regulatory approvals before he can formally take up the position.
He will work closely with head coach Régis Le Bris and the rest of Sunderland’s first-team staff, replacing James Brayne, who has left his role as an assistant coach at the club.
Herdal spent five years working with FC Nordsjælland’s first team after progressing through the club’s academy. His responsibilities included set-piece preparation and analysis, areas in which Sunderland have now added a specialist to their coaching operation.
His departure from the Danish club followed a decision not to extend his contract, which ended in May.
The move also reunites Herdal with the demands of international football. He worked with Denmark’s national team during the autumn of 2025, serving as an assistant coach with particular responsibility for set pieces.
That experience gives Sunderland a coach familiar with both the detailed preparation required at club level and the tactical demands of international competition.
Set pieces have become an increasingly important part of elite football, with clubs devoting considerable attention to attacking routines, defensive organisation and the analysis of opponents’ weaknesses.
Herdal’s appointment adds dedicated expertise in that area as Sunderland continue their work under Le Bris.
The club’s confirmation made clear that the appointment remains conditional on the outstanding approvals. No final start date was specified.
Once those requirements are satisfied, Herdal will join the coaching group responsible for preparing Sunderland’s first team for Premier League fixtures.
His arrival follows Brayne’s departure and represents a change in the composition of Le Bris’ backroom staff, with Sunderland bringing in a coach whose recent work has centred on set pieces and performance analysis.
The move also extends a professional career built largely at FC Nordsjælland, where Herdal developed from an academy-level role into a specialist position with the senior team.
Sunderland will now await the completion of the necessary formalities before the Danish coach can begin his new job.