The long-awaited designated player from Argentina worked out with the Impact for the first time on Thursday, a day after his old club, San Lorenzo, pulled off a victory without him over Uruguayan side Nacional Asuncion in the Copa Libertadores final.
"I'm very happy for San Lorenzo, but now I'm thinking about the Impact," the 29-year-old said through an interpreter. "I'll do everything I can to help this team."
Piatti signed with Montreal on July 2, but the Impact agreed to let him stay for San Lorenzo's climb through the final stages of the Copa Libertadores, the South American champions league.
However, the sport's governing body FIFA turned down his request to stay with Pope Francis's favourite team beyond the Aug. 8 close of the international transfer window. So Piatti played in the first leg of the final last week, but was not allowed to play in the return leg in Buenos Aires.
Coach Frank Klopas confirmed that Piatti signed a three and a half year deal with the Impact.
The midfielder's skill and his ability to play on the left wing or in the middle will be welcome on a team that sits last in Major League Soccer at 3-14-5.
But how much he can help this season remains to be seen. Newcomers to MLS tend to need a half-season to adjust to the travel and the physical style of play. Klopas called him a player the team can build around in the next few seasons.
He will likely see some action in Montreal's home game Saturday against the Chicago Fire and is ready to accompany the side to El Salvador next Wednesday for a CONCACAF Champions League game against CD FAS.
"I think the adaptation is not going to be a problem," said Piatti. "I know the team is having a bad season. I'm ready for the challenge."
Piatti sent a chill through Impact fans' hearts last week when he told an Argentine reporter he hoped eventually to play with an American MLS team like New York or Miami. On his arrival on Wednesday, he said his words had been taken out of context and that he was glad to be in Montreal.
Having a new player from a winning program may help boost spirits on the Impact, who have lost seven league games in a row.
"Any time you bring in a quality player like that it lifts everybody on the team," said Klopas. "You could sense a bit of that (at practice).
"But we have to understand it's one player. He'll make us better, but our whole team has to lift our game a bit."
The five-foot-11 Piatti, who speaks Spanish and Italian, had been on the Impact's radar for two years. An attacking midfielder, he played for St. Etienne in France and Lecce in Italy before returning to Argentina in 2012 with San Lorenzo, where he scored 12 goals in 54 matches.
"Just having him on the field with the ball, with his ability to beat players and put the opposing team under pressure, can help us a lot," said Klopas. "There's a period of adaptation for every player, but he brings a lot of quality and I think instantly he's going to add a lot to our team."
His new teammates liked what they saw of Piatti in practice at Saputo Stadium. He played mostly on the left side during a scrimmage, in the position normally held by fellow Argentine Andres Romero. It would not be a surprise if Piatti subbed in for Romero, or vice versa, against the Fire.
"I'm very happy he's finally here," said defender Hassoun Camara. "It's been a long time that we were expecting him.
"But we know he doesn't have to be the hero. We don't have to put a lot of pressure on him. He's here to help the team".
He is the team's second DP along with 38-year-old striker Marco Di Vaio, who is expected to leave at the end of the season. Another DP, midfielder Hernan Bernardello, left last month to join Mexican club Cruz Azul.
Di Vaio said he's looking forward to having a talented midfield player to help create offence. He said Piatti's personality and confidence showed in the fact that he has taken No. 10, which is normally reserved for a team's offensive leader and best attacking midfielder.
"Everyone in Montreal has been waiting for a number 10," said Di Vaio. "I hope he can do something big for us."