Who’d be a Spurs fan right now?
Mauricio Pochettino’s side began last week with dreams of a double, but having seen Costa return to form with two goals at Stamford Bridge in a match which saw Eden Hazard and Gary Cahill also score, any prospect of them overhauling the leaders now looks a pipe dream with little more than three weeks of the season remaining.
“It feels like a massive step, to be honest,” said Chelsea defender Gary Cahill.
“It’s the first time in a long time that we’ve played (before Tottenham) so we knew how important it was to get the win. We’re delighted today, we played well and deserved the win.”
Despite the result, Chelsea were not necessarily at their best against Southampton — and there’s an argument to say the league leaders haven’t been on top form for quite some time — but there were still a number of huge positives for Antonio Conte’s side as they took their points tally to 78 with five to play.
Number one, of course, is the result itself, a vital win going into a difficult away game at Everton on Sunday which would have looked pretty daunting if things had gone wrong here.
Secondly, two long-awaited goals for talisman Costa — a player who has struggled to hit the heights he reached earlier in the season — was much needed.
Thirdly there was an excellent performance in midfield from Cesc Fabregas after he was chosen ahead of Pedro, responding with two assists and a dominant display.
It had certainly been a big week for Chelsea in the run-up to this fixture; a high-octane FA Cup semi-final victory over Spurs at Wembley to earn a crack at Arsenal in the final, and a PFA Player of the Year award for midfielder N’Golo Kante leaving Conte’s side on a high and ready to finish the job in the Premier League too.
But Southampton, who had a full 10 days to prepare for the match in west London, are tricky opponents and showed, in spells, why they are close to being a threat to the top eight in future.
So, even though Chelsea went ahead after only five minutes, when Costa raced onto a Fabregas through ball and set up Hazard to drill home low, there was never a sense at Stamford Bridge that this was going to be an easy night.
The Saints were level by the 24th minute, a goal which came at the end of an extended period of possession from the visitors who at times bossed the game in those early stages.
Chelsea will be disappointed, too, at the way it was conceded — a deep corner finding Manolo Gabbiadini unmarked at the far post. The striker’s shot was saved by Thibaut Courtois but Oriol Romeu, a former Chelsea player, had a simple task to tap home for 1-1.
That goal means Chelsea have now gone 11 Premier League games without keeping a clean sheet (and bearing in mind they conceded only two times in the first 12 games after switching to a 3-4-3 formation that’s a significant statistic).
But thankfully for Conte, there appears to be enough resolve and quality in his side to mean that particular failing may be a bigger concern for next season than for this.
Nerves were settled on the stroke of half-time as Kante’s cross was headed back across goal by Marcos Alonso for Cahill to score with an excellent downward header, his seventh of the season.
Then came the goal the Bridge has been waiting for — Costa heading home a cute Fabregas cross in the 53rd minute.
It was the striker’s 23rd goal for club and country this season but his first for Chelsea since March and first at home since a 3-1 victory over Swansea in February.
He added another, from a boisterous run and shot, late in the game and his return to form could not have come at a better time — with Ryan Bertrand’s last-minute header proving immaterial.
The games ahead for Chelsea suggest this result could be vital in their battle to win the title — Sunday’s trip to Goodison is followed by a home game against relegation favourites Middlesbrough, a trip to West Brom, a match against Watford at the Bridge, and a home finale against Sunderland, who will likely be relegated long before arriving in west London.
Tottenham’s run-in, which includes Sunday’s North London derby against rejuvenated Arsenal, looks far tougher and so no wonder Chelsea fans were celebrating.
They were even treated to five minutes of John Terry at the end as the club captain was ushered on in place of Victor Moses. You can be bet the veteran centre-half will be muscling in on a trophy party pretty soon.
Courtois 6, Azpilicueta 6, Luiz 7, Cahill 7, Alonso 6, Matic 6, Fabregas 8, Kante 7, Moses 7 (Terry 86; 6), Hazard 7 (William 90), Costa 8.
Begovic, Ake, Pedro, Batshuayi, Chalobah.
Forster 7, Soares 6, Yoshida 6, Stephens 6, Bertrand 7, Davis 7, Romeu 7, Tadic 6, Boufal 6 (Redmond 68; 6), Ward-Prowse 7 (Long 82; 6), Gabbiadini 6 (Rodriguez 86; 6).
Hassen, Clasie, Caceres, Hojberg.