Green shoots of hope have been few and far between for troubled Spanish champions Barcelona this season but the emergence of teenage starlet Lamine Yamal is the clearest.

The 16-year-old winger could prove crucial in the Champions League last 16 second-leg clash with Napoli on Tuesday at the club's temporary Olympic Stadium home.

Yamal became the youngest player ever to feature in the Champions League knock-out stages as he impressed in the 1-1 first-leg draw in the south of Italy.

Robert Lewandowski opened the scoring but Barcelona were pegged back by Victor Osimhen, leaving the tie finely poised.

Off the pace in La Liga and out of the Copa del Rey, a deep run in Europe is the best Barca can hope for this season.

Yamal made the difference for them on Friday against Real Mallorca in La Liga, scoring a sensational goal out of nothing to snatch Barcelona, third, a 1-0 win.

It led Mallorca coach Javier Aguirre to label the young Spain international a "rat" and a "scoundrel" -- in the most positive sense possible.

The grizzled Mexican coach compared Yamal's emergence to Barcelona's best ever player and record goalscorer Lionel Messi.

"The first time I saw Messi was with Barcelona's youth team, I saw him for five minutes and he was a rat, he did not stop scoring goals," said Aguirre.

"Lamine looks like a rat too, the scoundrel."

With veteran striker Lewandowski playing inconsistently and winger Ousmane Dembele departing for Paris Saint-Germain last summer, Yamal has become a vital source of goals and inspiration for Barcelona.

The forward has netted six goals and provided seven assists in 37 appearances across all competitions this season, many as a substitute.

In recent weeks he has become an essential component for coach Xavi Hernandez, starting in nine of his last 10 appearances.

Yamal hit a brace to rescue Barcelona a 3-3 draw against Granada in La Liga in February, coincidentally against the same side he netted in October to become the division's youngest ever goalscorer.

The 16-year-old is Barcelona's most dangerous player, fast and one of the few natural dribblers they have at their disposal.

At times in matches the Catalans already seem dependent on him -- lacking creativity in other areas, Barcelona seek Yamal and ask him to make the difference.

That was the case with Messi too, although comparisons with arguably the greatest player of all time would be unfair on a player just beginning his career.

"Comparisons don't help him, because he is totally different, anyone who has been compared with Messi comes out losing," Xavi told reporters Friday.

"There are moments in which he has flashes of Messi, because he's left footed playing on the right and comes inside, but the comparison with the best player in history is not good, because he will lose."

Yamal became the youngest player to feature in a Clasico when facing Real Madrid in October, and also the youngest player to play for and to score for Spain in September.

With three of Barcelona's key midfielders -- Frenkie de Jong, Pedri, and Gavi -- out injured, it heaps more pressure on Yamal to produce something special to take the team through. So far, Yamal has shown he can handle it.