Nicasio, 31, will be a free agent following the season, and was unlikely to return. Meanwhile, Alvarez, 22, at least has a chance to develop into a piece of the Phillies' future.
He hit .247 with 11 doubles, one triple, four home runs, 26 RBIs and a .702 OPS in 209 plate appearances with Double-A Springfield. He missed much of the season with an ankle injury, but posted a .795 OPS in his final 17 games with Springfield.
But last season with Class A Advanced Peoria, he hit .323 with 36 doubles, six triples, six home runs, 59 RBIs, 36 stolen bases and an .879 OPS. He led the Cardinals' farm system in doubles and stolen bases.
MLBPipeline.com said Alvarez "has the chance to grow into more power, but he might be more of a line-drive, doubles-type hitter because of his approach. Alvarez is an above-average runner with excellent instincts that allow him to be a threat on the bases. He has a very strong arm, but he needs to work on his footwork and hands to be a more effective defender at second."
The Cardinals placed Alvarez on the 40-man roster last year to protect him from the Rule 5 Draft. He takes Nicasio's spot on the 40-man roster.
Todd Zolecki has covered the Phillies since 2003, and for MLB.com since 2009. Follow him on Twitter and Facebook and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.