London - Diego Costa has ended his seven-game drought but the Chelsea striker's 18th Premier League goal of the season was not enough to secure victory as the leaders were held to a 1-1 draw by Southampton at Stamford Bridge on Sunday.
Jose Mourinho's side were desperate to bounce back from their midweek Champions League exit against Paris Saint Germain and take advantage of Manchester City's surprise defeat against Burnley on Saturday.
But Dusan Tadic's 19th penalty cancelled out Costa's 11th minute opener and denied the Blues the chance to establish an even more commanding lead over the chasing pack.