The Blues took advantage of a release clause in the region of £5m to sign the highly-rated prospect from Barcelona in the summer.
Although the 18-year-old came off the substitutes' bench against Manchester City on the opening weekend of the season, he had been primarily earmarked for game time in the Conference League.
On Thursday night, Guiu took his tally in the competition to six goals with a hat-trick during a 5-1 victory over Shamrock Rovers, making him the leading goalscorer in the tournament.
Nevertheless, speaking to reporters at a press conference after the game, Maresca hinted that the prospect will remain on the periphery of the squad.
"We forget the age"
While the Spain Under-19 international turns 19 at the start of January, the Italian indicated that he has no plans to rush his development.
As quoted by football.london, he said: "With Marc the problem is that sometimes we forget the age. He's the same age as Joshua Acheampong, Ty [George].
"He already scored five six goals in this competition, and since we started he's working well, he's taking his chance, and he knows that with Nicolas [Jackson] there, with Christo [Nkunku] there, it's not easy for him.
"But it's important that he continues to work in the right way."
Did Guiu make the right move?
With Barcelona in the market for a long-term replacement for Robert Lewandowski, it seemed the logical move to do everything possible to retain Guiu's services when they had the chance.
However, they were ultimately powerless once his release clause came into play and the player had his sights set on a move elsewhere. Furthermore, the La Liga giants stood to benefit from cashing in on a homegrown talent when needing to boost their financial position.
Guiu agreed to move to Chelsea on the basis that he would not be loaned out to sister club Strasbourg, and the decision is currently paying off for all involved.
A total of 442 minutes have been accumulated across 10 appearances in all competitions. At a team on the current trajectory of Chelsea, that is perhaps more than he would have anticipated.
Although there is an acceptance that Nicolas Jackson and Christopher Nkunku are ahead of him in the pecking order, Guiu knows that chances could come off the substitutes' bench if and when more injuries take effect.
However, if he continues to showcase his predatory instincts in front of goal, offers will inevitably follow, whether that be a permanent deal for Chelsea to make a substantial profit or a loan to further his development.
Written by
Darren Plant