Diego Costa's 10th Premier League goal of the season gave Chelsea a 1-0 victory over Middlesbrough - and sealed top spot in the table.
Diego Costa sealed a 1-0 win for Chelsea over Middlesbrough at the Riverside Stadium to send Antonio Conte's side top of the Premier League.
The Spain international turned home his 10th top-flight goal of the season from a corner late in the first half to secure a sixth win and clean sheet in a row for the division's form side.
Chelsea scored 16 goals in their previous five league games but were kept at arm's length early on by Aitor Karanka's disciplined side, with Victor Valdes' save from Pedro the only opportunity of note.