A day after pledging his full commitment to Liverpool despite his sadness at their failure to offer him a new contract Mac Allister duly delivered with a brilliant winning goal against Atlético Madrid.

The Argentina international stressed he would give 100% to the cause despite the perceived slight and was true to his word with a sweetly-struck left-footed effort from 20 yards.

That came after Dominik Szoboszlai's equaliser had cancelled out Liverpool nemesis Marcos Llorente's fifth goal in three Anfield visits as head coach Andoni Iraola celebrated his managerial Champions League debut with a 2-1 win.

Mac Allister's all-round performance was one of many positives, as was the full debut of £123 million ($166m) signing Bradley Barcola who, with better finishing would have had a hat trick before he was forced off with an apparent calf injury.

Florian Wirtz, one of the great hopes of last summer's window, continued his improvement and seemed to find the France international's wavelength pretty quickly.

Barcola, back-to-back Champions League winner with Paris Saint-Germain, started on the right rather than his preferred left with Cody Gakpo left out as a precaution and twice shot at goalkeeper Jan Oblak from promising positions in the first half.

However, his most glaring miss came five minutes after the break when from Wirtz countered and sent him racing through the middle.

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But the Kop's cheers as he rolled a shot past Oblak towards an empty net were cut short as the ball drifted past the post.

Fortunately it did not prove costly as Liverpool's high press from the restart saw possession quickly regained and when the loose ball bounced out of the penalty area Mac Allister blasted home with his weaker left foot.

Barcola's apparent injury would be a setback both individually and collectively as his much-needed pace was one of the main reasons he was the club's main transfer target this summer.

And if Gakpo remains out for the weekend visit of Fulham it leaves Iraola with only the relatively inexperienced Rio Ngumoha, who started on the left, and his second-half replacement Víctor Muñoz.

A lack of depth in the squad was evidenced by four academy players on the bench - not including the 19-year-old Trey Nyoni who is now a first-team regular.

The 18-year-old Ngumoha showed flashes of his mercurial talent against wily European operators and another plus was the performance of on-loan former Barcelona captain Ronald Araújo, primarily a centre-half, in his second start at right-back.

His experience brought some much-needed composure on a night when there was potential to fall foul of the visitors' gamesmanship.

But it was his cheeky backheel to Szoboszlai five minutes before half-time which brought the equaliser.

Left-back Milos Kerkez won the ball in Atleti territory and although Barcola squandered the chance Wirtz recovered the ball, allowing Araujo to claim the assist.

That move was the highlight of Kerkez's night as he again struggled with his positioning and awareness, contributing to the opening goal.

Julián Álvarez, making his first start of the season after a summer transfer saga, was given too much time to thread a simple pass behind Virgil van Dijk and Llorente ran past Kerkez to clip a shot past Alisson - again.

But a first victory after conceding the first goal since January was yet another positive.