According to a baseball source, the Red Sox interviewed former Oakland pitching coach Curt Young on Monday about the vacancy for the position of pitching coach that was created by the departure of John Farrell, who left to become the manager of the Blue Jays. Young, according to the source, was the most impressive of the external candidates with whom the club has talked thus far.

Young spent the last seven seasons as the Athletics pitching coach. In 2010, the young Oakland staff led the American League with a 3.58 ERA. But after 27 years in the A’s organization as a player and coach, Young turned down the team’s offer on Sunday, and he appears to be a strong early candidate to succeed Farrell.

That said, the interview process remains ongoing for the Sox. Later this week, the team will interview a pair of internal candidates: Mike Cather, who served as an advance scout in 2010 after three years working in Double-A Portland (2007-09) and one with High-A Wilmington (2006), and Ralph Treuel, who has spent the last four years as the organization’s roving minor league pitching instructor. Treuel also spent part of the 2006 season as the Sox bullpen coach, and served briefly as the team’s pitching coach in Sept. 2001.