Alvarez, a 23-year-old third baseman who was the No. 2 overall pick in the 2008 draft, was hitting .277 with 13 home runs and 53 RBI in 66 games for Triple A Indianapolis this season.
The Pirates fan base has been salivating about his possible arrival in Pittsburgh. He is the most ballyhooed Pirates' power-hitting prospect since Barry Bonds joined the Bucs in 1986.
Alvarez, general manager Neal Huntington indicated, will step in as the team's everyday third baseman immediately. Andy LaRoche who had been the club’s primary third baseman will slide into a utility role.
"We've envisioned this for the organization," Pirates manager John Russell said. "He's done some great things. We'll continue that process. I think he's going to be a big boost for our club."
"This is the first step in a long journey, hopefully," Alvarez offered. "It is a big one. All those practices and all those long drives, it pays dividends in situations like this. ... I am at a shortage for words just trying to explain what this feels like right now."
His Pirates’ teammates just like the fan base are anxious to see Alvarez in the lineup.
"He's that guy that when he comes up to bat, any time possible he can hit a home run," Andrew McCutchen said. "He's that bat that we're looking for. He's going to help this lineup out a lot. We can't wait for him to get here."
Alvarez will have a lot of pressure when he arrives in Pittsburgh, he is viewed by many as the savior of the franchise.
"It is a big step, but it isn't the last one for me to take," Alvarez said. "It starts right now. I have a huge responsibility."
The Pirates will have to make a corresponding roster move to clear a space for Alvarez on the 25-man roster. Huntington said that would be done on Wednesday. He did not specify whether a position player or pitcher would be coming off.