The 20-year-old was signed from Sevilla in the summer as one for the future, and would have impressed manager Brendan Rodgers who was in attendance on Tuesday night.
Jack Dunn and England international Raheem Sterling scored the others, while Alejandro Rodriguez-Gorrin and David Moberg Karlsson netted for Sunderland.
The timing of Alberto’s hat-trick could not be better as Liverpool await news on Coutinho’s injured shoulder, which forced him off during Monday’s 2-2 draw with Swansea.
Rodgers confirmed after that game the Brazilian would require a scan, the results of which are yet to emerge.
At this stage it would be a surprise if Coutinho was declared fit for the Saturday visit of Southampton to Anfield, which would leave Rodgers needing to adjust his attack.
Luis Suarez is unavailable as he serves the final match of his 10-game suspension, while Iago Aspas is taking time to settle in English football after a promising Premier League debut against Stoke.
The former Celta Vigo man will likely get the nod at the weekend, but Alberto—a £6.8 million signing from Sevilla—did his chances no harm as he led a thrilling comeback for Liverpool’s youngsters.
His first goal featured excellent approach play with Raheem Sterling, exchanging a clever one-two before side-footing home. The second needed a slice of luck as Alberto converted at the second attempt after rounding the keeper, while the third came from the spot when Sterling was upended.
The Spaniard’s style of play arguably makes him a preferable option to Aspas, who likes to operate through the centre, linking play with his back to goal. Daniel Sturridge is currently Liverpool’s main man and needs to remain the attack’s focal point.
Alberto connects play from a deeper position and likes to keep his head up. It was noticeable that Liverpool could not knit midfield to attack when Aspas replaced Coutinho at Swansea, something Alberto would offer.
Liverpool will be protecting their undefeated record against Southampton, having taken 10 from a possible 12 points to top the table.