Christian Pulisic hit the first hat-trick of his career as Chelsea crushed Burnley 4-2 on Saturday while Manchester City overcame a sluggish start to beat Aston Villa and increase the pressure on Liverpool.
Away from the top end of the Premier League table, pressure is mounting on Everton boss Marco Silva after the Merseysiders' fifth defeat in their past six league games.
US international Pulisic, who was without a goal for Chelsea since his £58 million ($74 million) move from Borussia Dortmund, had not started a Premier League match for Frank Lampard's young side since August.
But he made an emphatic case for himself at Turf Moor with a "perfect" hat-trick -- scoring with his left foot, right foot and head.
The 21-year-old capitalised on some indecision from Burnley to drive into the penalty area, producing a stepover before steering a low left-footed shot into the corner of Nick Pope's net midway through the first period.
The former Dortmund winger doubled his tally for the Blues with a second goal just before half-time, benefiting from a big deflection off Ben Mee, and grabbed his third with a second-half header.
Willian added a fourth for rampant Chelsea in the 58th minute to take the score to 4-0 and despite late goals for Jay Rodriguez and Dwight McNeil, the visitors avoided further shocks to win 4-2.
"It's my first professional hat-trick so I nearly forgot the match ball," Pulisic told the BBC. "Luckily my teammates helped me out.
"I just want to be on the field, help the team and make an impact. I didn't think it would be super easy. But I have come on a few times the past few weeks and was happy to start today. It was a special day."
Lampard defended his cautious handling of Pulisic.
"He had a week's break this summer," the Chelsea boss told Sky Sports.
"He arrived for a big price and wanted to come straight back in but at the same time why am I going to throw him in? So I have to do it in the right way and get the best out of him. I'm delighted for him."
The victory consolidates Chelsea's position in the top four. They have 20 points, the same number as third-placed Leicester, whom they trail on goal difference.
In the early kick-off, a frustrated Pep Guardiola watched his side recover from a tepid first half to defeat Villa 3-0 and close the gap on Jurgen Klopp's Premier League leaders to three points.
"The first half we played football but we don't play in the way we should play," Guardiola said, after second-half goals from Raheem Sterling, David Silva and Ilkay Gundogan.
"We were better in the second half. I don't know if it was because of the early goal. In the second we play in the way we normally do but we have to try and play 90 minutes. We played just 45."
Liverpool are under pressure to beat Tottenham at Anfield in Sunday's clash between last season's Champions League finalists.