Chelsea completed the league stage of the Conference League with a perfect record as Marc Guiu scored a first-half hat-trick to seal a 5-1 win over League of Ireland side Shamrock Rovers at Stamford Bridge.

The 18-year-old former Barcelona striker is not yet in head coach Enzo Maresca’s starting XI in the Premier League but has been selected for the fourth time in Europe. He showed a poacher’s instinct to bury the visiting team, twice intercepting passes back to the goalkeeper and scoring a goal before scoring a fine header for the third time.

Kiernan Dewsbury-Hall also scored, as did Marc Cucurella for the second time in as many games. Chelsea confirmed what had been clear for a long time: they are far too strong for the teams they faced in the first phase of the third European competition.

The defeat was a first in Europe this season for Shamrock, who left west London with the consolation of a place in the play-off round in February, as well as the memory of Markus Poom’s goal that briefly tied the score at 1-1 in the first half -The equalizer was made possible and the victory was a foretaste of a big surprise. Chelsea had more than 80% possession in the first 25 minutes, but it took a defensive error to take the lead.

Renato Veiga threw a looping ball forward for Tyrique George to chase. Darragh Burns went first but his header to his goalkeeper was completely misjudged, allowing Guiu to sneak in and give Chelsea the lead.

The visitors reacted quite courageously. Chelsea goalkeeper Filip Jorgensen flew towards his top corner to keep out a shot from Johnny Kenny as Shamrock went bust. After the resulting corner, Shamrock briefly left his supporters dreaming.

Dylan Watts’ cross landed with his head on the edge of the penalty area, where Estonian international Poom – whose father Mart played for Derby here in the 1990s – waited to flick the ball back into the goal, his shot coming off the heel of Cesare Casadei rebounded and raced past Jörgensen.

It was a memorable moment for Shamrock in their European adventure, which made the way they conceded the next goal all the more bitter. Daniel Cleary offered Guiu another gift. His pass back to Leon Pöhls was undershot and didn’t even get close to his goalkeeper, but had the perfect trajectory for Guiu, who got there first and played around Pöhls to make it 2-1.

The hosts scored their third goal after 40 minutes. Cucurella passed the ball to Christopher Nkunku, who was knocked down by Roberto Lopes. Before the referee could award a penalty, Dewsbury-Hall had fired the loose ball into the bottom corner for his second Chelsea goal.

Guiu completed his hat-trick with the final action of the first half, rising highest in the penalty area and firing Noni Madueke’s cross into the corner. Cucurella cut inside his defender before firing into the near post just before the hour mark to make it 5-1.

Maresca sent academy graduates Samuel Rak-Sakyi, Harrison Murray-Campbell and Harvey Vale to get a taste of European football and the then 18-year-old winger George almost opened his Chelsea account, which was on the line from Rovers -Captain Lopes was repelled.