safc.com profiles three of the 20 players to play for the Black Cats and the Blues.Emerson Thome
Brazilian defender Emerson Thome signed for Chelsea from Sheffield Wednesday in 1999 but only spent nine months at Stamford Bridge after finding it difficult to break up the central defensive pairing of Marcel Desailly and Frank Leboeuf.
The Blues let Thome join Sunderland - having played just 21 league games for Chelsea - at the start of the 2000-01 season and the Brazilian went on to make 52 appearances in an injury-hit spell on Wearside.
He made his Sunderland debut in a 1-1 draw with West Ham United at the Stadium of Light in 2000 and went on to score twice in Sunderland colours; scoring the winner in a 1-0 win over Coventry City in 2000 before grabbing a late equaliser in 1-1 draw with Aston Villa on New Year's Day in 2002.
After his time with Sunderland finished, Thome joined Bolton Wanderers before spells with Wigan Athletic and Derby County.
Oxford-born winger Clive Walker began his career at Chelsea and made 224 appearances for the Blues, scoring 65 goals after progressing as an apprentice through to the first team.
Clive played a big role in many important matches for the Blues, noticeably his performances against Liverpool in the 1978 and 1982 FA Cup and his last minute winner against Bolton in the penultimate game of the season that ensured Chelsea’s Second Division status.
Walker joined Sunderland in July 1984 and spent 18 months on Wearside as the Black Cats reached the League Cup final only to be defeated 1-0 by Norwich City.
The finest moment of his spell with Sunderland was his hat-trick in a 3-2 win over Manchester United at Roker Park in a season where he finished as the club’s leading scorer with 14 goals.
Dutch midfielder Bolo Zenden moved to Chelsea in 2001 after a colourful start to his career saw him win league titles with PSV and Barcelona.
Zenden made 59 appearances in two seasons at Stamford Bridge as the Blues made the FA Cup Final in 2002 only to be defeated by Arsenal.
Bolo left for Middlesbrough in 2003 and spells with Liverpool and Olympique Marseille followed before he moved to Wearside in 2009.
A fans’ favourite at the Stadium of Light, Zenden was fondly remembered for his celebration with Gyan Asamoah in the famous 3-0 away victory at Chelsea in 2010.
Goals against Tottenham Hotspur, Bolton Wanderers and West Ham United, in his last game for the club, were other particular highlights of his spell at Sunderland.
Bolo was assistant manager to Rafa Benitez at Chelsea before joining the coaching staff at PSV this season.