Shortstop Jorge Polanco and the Minnesota Twins are finalizing a contract extension that will cover seven years and guarantee around $25 million, a league source with knowledge of the deal told ESPN on Thursday.

The contract will buy out Polanco's last pre-arbitration season, all three arbitration seasons and up to three free-agent years. At least five years will be guaranteed, and the overall value could jump if the Twins exercise the club option that can take the deal to a seventh season.

Polanco, 25, has been a strong if not entirely steady presence in the middle of the Twins' infield. Minnesota was discussing an extension with the switch-hitter last winter before he received an 80-game suspension after testing positive for a banned substance that he said came from a tainted supplement.

In 77 games after his return, Polanco hit .288/.345/.427 with six home runs and 42 RBIs.