He impressed in a 3-1 win for United's U23s over their Saints counterparts.
United led 1-0 at the break on a brisk night at Leigh Sports Village thanks to a first-half effort from Swedish winger Anthony Elanga.
And within 30 seconds of the restart, Pellistri doubled the home side's advantage.
The former Penarol kid combined with Shola Shoretire, who produced an outstanding pirouette midway inside his own half before returning the through pass, before racing through and coolly finishing with his right foot.
After Michael Obafemi had reduced the arrears, Pellistri almost notched his second, hitting the crossbar, before Arnau Puigmal made the result safe in stoppage time.