But the Italians, who entered the GUINNESS PRO12 clash with three wins from their last five matches in all competitions, responding with two Dries van Schalkwyk tries.
Scarlets were under pressure, as Maselino Paulino was sent to the sin bin, but Steven Shingler slotted a late penalty to ensure Zebre not only lost but also missed out on a losing bonus point.
Guidi said: "We adapted badly to the strong wind, as shown by zero out of six for kicks to the corner in the first half.
"I am happy with the middle part of the game when the team found tranquillity and played well.
"Our young players made it tough for a side which consisted of two-thirds of the Welsh national team.
"The deserved bonus point was tight, but we finished with a defeat and no points. We paid dearly for starting with such a handicap."
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Guinness PRO12 Zebre News
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