The 20-year-old struck in the 56th minute to double Boca’s advantage and add to the lead already given to them in the third minute by Ramon Abilia.
The result leaves them top of the Supeliga table, three points above Mac Allister’s former club, Argentinos Juniors.
Percy Tau came on for the final 30 minutes of a 2-0 win for Club Brugge in a 2-0 win over KV Oostende on Friday.
It was a day to forget for Jurgen Locadia and Hoffenheim in the Bundesliga, following a 5-1 defeat at home to Mainz.
Leo Ostigard and Viktor Gyokeres both played the duration of a 3-1 defeat for FC St Pauli against FC Erzgebirge Aue in Bundesliga 2
George Cox was also on the receiving end of a 3-1 scoreline for Fortuna Sittard against PEC Zwolle in the Dutch Eredivisie, while Anders Dreyer came on for the final two minutes of Heerenveen’s 2-1 defeat away at PSV Eindhoven.
Jan Mlakar was on the wrong end of a 2-1 defeat for Queens Park Rangers against Fulham at Craven Cottage on Friday. Jordan Hugill gave Rangers the lead, before Aboubakar Kamara netted a brace to give the hosts all three points.
Elsewhere in the Championship, Ben White was on the winning side for Leeds United in a 2-1 victory away at Luton Town on Saturday. Patrick Bamford’s opener for Leeds was cancelled out by a James Collins header, before Matt Pearson’s late own goal gave the visitors all three points in Bedfordshire.
It was also a good day for Max Sanders and AFC Wimbledon in League One, who claimed a 1-0 win over Gillingham at Kingsmeadow, courtesy of Scott Wagstaff’s goal in the 19th minute.
But it was a different story up at the Crown Oil Arena, where Robert Sanchez and Rochdale fell to a 3-0 defeat at home to Portsmouth. Ronan Curtis’s brace and a goal from Ryan Williams secured all three points for Pompey.
James Tilley played the full 90 minutes for Yeovil Town in a 3-3 draw away at Wrexham on Saturday. A Rhys Murphy hat-trick was not enough for the Glovers to take all three points, as goals from Akil Wright, Paul Rutherford and Bobby Grant claimed a share of the spoils for the hosts.
Meanwhile, in the Isthmian League South East Division, Kacper Lopata played the full 90 minutes for Whitehawk in their last-gasp 3-2 win at Ashford United on Friday night. Rhyle Ovenden struck in stoppage time to give the Hawks a memorable win.