A try from 20-year-old replacement Steffan Hughes was the only bright spot of a stop-start game. Hughes crashed onto Aled Davies’ pass 15 minutes from time after the Scarlets’ scrum shoved the Italians onto their heels to complete the home side’s comeback having trailed 13-12 at half-time.
Stefan Evans saw his clearance kicked charged down by Zebre lock Valerio Bernabo for the game’s opening try. But outstanding work at the breakdown by James Davies and Rob Evans as well as the boot of Shingler proved decisive.
Scarlets were already without 18 players through international duty and, more tellingly, injuries when they lost Kristian Phillips inside three minutes.
That prompted a first start of the season for Wales Under-20s captain Hughes but the youngster saw precious little ball a tight contest that struggled to get past the set-pieces, which proved as unpredictable as the swirling rain.
Fittingly it was a comedy of errors that led to the opening try. Shingler had kicked his team back in front, 9-6, when Scarlets failed to gather the re-start.
Brendan Leonard’s a drop goal was tipped in flight, playing Bernabo onside. The second-row was then in place to charge down Evans’ clearance and stretched out to score. It was symptomatic of a game desperately lacking any shape or order.
Shingler reduced the deficit to 13-12 and 20-year-old Evans did well to recover from his error, sweeping onto Leonard’s kick with No8 Andries van Schalkwyk baring down.
Two further penalties put Scarlets back in front before both sides were reduced to 14 men in the space of three minutes. Zebre prop Dario Chistolini, for infringing at a scrum, and then Earle at a lineout, were binned.
Aaron Shingler stole a crucial throw just five yards from the Scarlets line and that proved a turning point. Scarlets edged up-field to score a try. Scarlets stole a march at a scrum and scrum-half Aled Davies picked his moment to send Hughes crashing over.
Hughes should have had a second but failed to collect Owen’s pass. Aled Davies narrowly missed out also in the final moments.