Leicester opened up a four-point gap in fourth place in the Premier League with a win over West Brom at King Power Stadium.
Three goals in the 13th minute of the first half did damage as striker Jamie Vardy got one and helped the other.
Defender Jonny Evans nodded in a reversed corner to make it 2-0.
In a game with many chances to score, Matheus Pereira of Castagne and Matheus Pereira of West Brom also hit hard in the first half.
Leicester’s victory is now four points adrift of Chelsea, who take the final spot in the Champions League with six games to go. The two teams meet in the league and the FA Cup final next month.
“I don’t think about other teams. We have to think for ourselves. We can only control ourselves,” said Leicester’s chief executive Brendan Rodgers.
“This team will sometimes lose games, but they are very loyal and want to get better. If you have that, it is a dream ticket. That’s all you can ask for as a coach.”
West Brom is on the brink of relegation as they are nine points adrift of safety and have a much lower goal difference than Burnley in 17th place.
Manager Sam Allardyce said his team “could not face” Leicester, who added that they were “just following Manchester City in that game.”
“You can see why Leicester is in the league and why they are in the FA Cup final,” he added. “Leicester is much better than Southampton and much better than Chelsea. They are like the best boys.”
The relentless Leicester ends an unforgettable week.
After booking their place in the FA Cup final on Sunday, Leicester could not finish the week in a better way.
They looked eager to get their feet in front of them – recording West Brom’s defense outside with balls from Youri Tielemans and driving runs from Vardy and Castagne.
Iheanacho and James Maddison both got chances in the first 10 minutes before the Tielemans played at Castagne and put it on the plate for Vardy to hit in the middle.
West Brom’s last defender Dara O’Shea of Iheanacho, blocked Leicester’s moment, but the comeback was temporary as Evans shook his head 2-0 within three minutes of Vardy’s opening.
Striker Vardy became a supplier when he jumped past his opponent and put Iheanacho for the third time in Leicester.
The goal came after West Brom’s Pereira and Leicester’s Castagne hit the post, and there could have been another goal for Iheanacho before the break, but he hit it more than six yards out.
Leicester’s inconsistent attack in the first half caused damage, and they still found plenty of space in the second half – Iheanacho saw O’Shea’s shot blocked in the box and a free-kick set by goalkeeper Sam Johnstone, while Vardy’s long chip sailed wide.
Rodgers also managed to oust Maddison, Vardy, and Wesley Fofana in Monday’s game against Crystal Palace.
Baggies’ ‘big escape’ is all but gone.
The back-and-forth victories of Chelsea and Southampton have given West Brom a glimmer of hope in their week-long battle to secure a place in Sheffield United.
Allardyce named the same side that beat Southampton, but the difference in performance was clear.
Leicester beat West Brom from the opening minute and could not recover in the first half, which could have seen many goals go their way.
Pereira’s corner slammed into the crossbar, Mbaye Diagne completely missed the chance on the edge of the box, and Matt Phillips’ strike went straight to the goalkeeper in a few cases at West Brom.
Substitutes Semi Ajayi, Hal Robson-Kanu, and Karlan Grant failed to impact the second half as Leicester came close to winning.
It means that any chance of a big break for West Brom is over – they have 18 points to play for but have only taken 24 this season.
‘Leicester has broken our defenses’ – they said
Leicester manager Brendan Rodgers on BBC Sport: “In the first half, I was not happy at all. We could have been more accurate in our passing. In the second half, we controlled the game.
“All in all, I am very happy as winning the Premier League has always been great. We were fine, but we could be much better. It would always be a great test. We have to control ourselves and our performance.”
West Brom manager Sam Allardyce at BT Sport: “Leicester were very good to us, in the first half in particular. We have tried to look forward to the two of them, and one of the main reasons for our recent results was our solidarity. Leicester is sad. We could not deal with them.
“It was a good second half. But we didn’t get much on the other side. In the end, we deserved to be beaten. You have to fix the basics, and those bases have left us. We need to win five of the six smells [by staying in the Premier League]. We will do our best.”