The Gunners signed the 18-year-old in a £6m deal from Brazilian club Ituano in the summer in a transfer that went under the radar compared to club record signing Nicolas Pepe.
Martinelli, though, has scored more goals than Pepe following his excellent performances in the Europa League and the Carabao Cup so far this season.
The 18-year-old scored twice in Arsenal’s 5-5 draw with Liverpool FC in the Carabao Cup fourth round last week.
Liverpool FC managed to progress to the League Cup quarter-finals, but Martinelli left a lasting impression on Klopp.
The German coach heaped praise on Arsenal transfer chief Edu for unearthing the Brazilian talent.
“It was not in this game only. I watch a lot of football, so I saw the Europa League games of Arsenal,” Klopp told Brazilian TV show Esporte Interativo, as quoted by the Daily Mirror.
“He’s 18 years old, right? So our scouting department is all over the world and stuff like this, but I think Edu gets all the credit for that signing – he came from… wherever.
“He’s really unbelievable. So young, looks so mature already, is a proper threat. Yeah, he looks like a really decent player.
“But I didn’t want to put any backpack [pressure] on his back with this thing [his earlier remarks] but I just really like good football players and obviously he’s a very good one.”
Martinelli has scored three goals and has made one assist in two Europa League games so far this season.
The Brazilian teenager has also netted four times in the Carabao Cup.
The summer signing has been made to wait for his first Premier League start after four substitute appearances under Unai Emery this term.
Arsenal are in fifth place in the Premier League table following their 1-1 draw with Wolverhampton Wanderers at The Emirates last weekend.
The Gunners signed six new players in the summer transfer window.
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