* Chelsea beat Middlesbrough 3-0 at Stamford Bridge
* Boro relegated, Chelsea one win from guaranteeing title
* Diego Costa scored in 23rd minute from Cesc Fabregas pass
* Marcos Alonso squeezed second goal under keeper 11 minutes later
* Nemanja Matic scored Chelsea's third after Fabregas chip
* Chelsea at West Bromwich Albion next, Boro host Southampton
LONDON, May 8 (Reuters) - CHELSEA 3 MIDDLESBROUGH 0
First-half goals from Spaniards Diego Costa and Marcos Alonso and a tap-in by Nemanja Matic propelled exuberant Chelsea to within three points of clinching the Premier League title on Monday and condemned Middlesbrough to relegation.
Costa got his 20th league goal this season, controlling a ball lofted into the area by compatriot Cesc Fabregas and neatly nutmegging keeper Brad Guzan. Two Spaniards were involved in the second goal, Cesar Azpilicueta feeding Alonso to score.
With Antonio Conte's team buzzing, Matic put away the third in the 65th minute to pile the misery upon Boro, who will join north-east neighbours Sunderland in the second tier next season.
Chelsea can claim the title in Conte's first season in charge even before nearest rivals Tottenham Hotspur play again if the west London side win at West Bromwich Albion on Friday. (Reporting by Clare Lovell; Editing by Ken Ferris)