The Stormers will be kicking themselves as they imploded in the final 20 minutes of their match against Benetton to hand the Italian side victory.
The visitors squandered an 11-point lead early in the second half to capitulate to a 22-18 loss in Treviso.
Benetton started life under Marco Bortolami with an impressive 22-18 home win over the DHL Stormers in a thrilling United Rugby Championship opener.
The lead changed hands on numerous occasions in Italy before teenager Tommaso Menoncello provided the crucial score with 10 minutes left to give Kieran Crowley’s successor a first victory in charge.
The Stormers, at the beginning of a four-week tour of Europe, only had to wait 72 seconds before they opened their account when centre Rikus Pretorius collected a grubber kick to cross over after two minutes at Stadio Monigo.
Debutant flyhalf Manie Libbok was unsuccessful with the resulting conversion and Rainbow Cup-winners Benetton soon produced a response.
After gaining early dominance in the forward battle, it was hooker Gianmarco Lucchesi who restored parity with 16 minutes played.
Nahuel Tetaz Chaparro combined well with Manuel Zuliani, who offloaded to Lucchesi and the Italy international produced an excellent finish to run in from close to 40 yards.
Argentinian flyhalf Tomas Albornoz, Paolo Garbisi’s replacement in Treviso, added the extras but his opposite number Libbok kicked his first points for the South Africans to give them an 11-7 lead at half time.
John Dobson’s side extended that advantage early in the second period when Pretorius turned provider, showing quick feet under the posts before he offloaded to fellow centre Ruhan Nel, who claimed an easy score.
Libbok’s latest successful kick had the visitors in control but Benetton fought back after they finally turned territory and possession into chances.
The bold decision to turn down an easy three points was vindicated near the hour mark when two of Benetton’s replacements combined, with Federico Ruzza claiming the lineout before Ivan Nemer went over after a driving maul.
An excellent conversion by Albornoz continued the momentum and when he nailed a penalty three minutes later, it narrowed the gap to one.
Bortolami’s men were in the ascendancy and, backed by a buoyant home crowd, the hosts moved in front.
Albornoz kept his cool after Benetton’s forwards had been held up on the line with Menoncello picked out on the left and the teenager finished off in the corner with 10 minutes left to give the Italians a hard-fought victory.