Roma coach Luciano Spalletti was left frustrated after their 1-1 draw with Europa League opponents Viktoria Plzen.
"We can and must do more and better," Spalletti told Sky Sport Italia.
“We had also gone in front and could've taken control of the game, because we had that opportunity, but instead it turned into a more physical match and that gave them the advantage.
“We conceded a goal that was absolutely avoidable. If you don't take control of a situation in these arenas, then the opposition will play heart and soul. We must be more relaxed and show greater character. We must do more."
Gerson was a surprise starter and was replaced at half-time.
“All considered he had a decent game, though he's excused to a degree because it was his first. In general those who don't play much need to make the most of these opportunities.
“You don't get five games to prove yourself in today's football. You get five minutes and five training sessions. Those who don't play as much need to show more hunger and intensity."