LONDON • If justification were needed for Chelsea's decision to spend a club-record £97.5 million (S$180.7 million) to bring Romelu Lukaku back to Stamford Bridge, the Belgian provided it with a master striker's goal on Tuesday.

In their first Champions League game since winning their second European Cup in May, the Blues were being frustrated by a well-drilled Zenit St Petersburg and it looked like a home stalemate was on the cards.

But with little over 20 minutes left, captain Cesar Azpilicueta delivered a peach of a cross towards Lukaku, who speared his header past goalkeeper Stanislav Kritsyuk for a 1-0 victory.

It was the 28-year-old's fourth Chelsea goal since joining from Inter Milan and offered further evidence that he could be the most important piece of manager Thomas Tuchel's jigsaw this season.

"It was an excellent header, a well-timed cross by Azpilicueta," said the German, who has transformed Chelsea since replacing Frank Lampard in January.

"That's why he is here. He likes to score and he's decisive for us."

Tuchel can often be an animated figure on the touchline but he was calm throughout Chelsea's opening Group H clash even when his side were struggling to open up the resolute Russians.

The hosts did not have a shot on target in the first half but picked up the pace after the interval, and Lukaku's predatory instincts were enough to break the deadlock.

"It was not frustrating. It was tough against very strong opponents. We had to work really hard. I felt a huge intensity from us which we brought to the game," Tuchel said.

"We struggled a bit to create chances and shots in the first half. In the second half, it was a bit easier to find spaces and shoot. It was a deserved win. Hard earned. It took us a while to make them tired but I liked what I saw."

While it was not a dazzling display by Tuchel's side, it was their 23rd clean sheet since his appointment - more than any other team in Europe's top five leagues in the same period.

It also showed that when they are not firing on all cylinders, they can grind out wins - especially with a poacher like Lukaku offering an old-fashioned route to goal.

"The performance from Romelu was not easy. We didn't create many chances for him, we did not create many deliveries. But he's the type of guy who doesn't lose confidence and belief.

"And that is why he is here and makes him a world-class striker," Tuchel said.

"It's not the only talent he brings, he brings belief and he takes the pressure off the shoulders of other guys around him."

On what Lukaku brought to the dressing room since rejoining for his second spell at the club after 2011-14, Tuchel added: "He was the type of profile we were missing, not just because of the talent but because of the personality.

"He is such a humble guy, a super communicator and that creates a certain energy around him and within the team."

REUTERS