The deal will officially be announced later on Friday.
Hill was fantastic last season for the Diamondbacks, when he posted a line of .302/.360/.522 with 26 home runs and 85 RBI. He won the Silver Slugger Award and led all National League second basemen with a WAR of 6.2.
Over the course of his career, though, Hill has been pretty inconsistent. He has a career line of .272/.327/.432, which are all numbers that are significantly lower than his 2012 output.
However, he has always been able to hit the long ball. With 124 home runs over eight seasons, he has been one of the most reliable second basemen in terms of power in the league.
The Diamondbacks were smart to lock Hill up before he hit free agency after next season.
The top two second basemen available next offseason were sure to be Hill and Robinson Cano. Any team in need of a second baseman would have been willing to overpay for either player, but Arizona was essentially able to get a more team-friendly contract by approaching Hill so early.
Cano is undoubtedly the best hitter available next offseason. He'll command top dollar (possibly upward of $200 million), and he will likely get it. Hill's much smaller extension still helps him out, though.
With no other viable alternatives to Cano, any team that wants to sign him will have no choice but to shell out the big bucks.
While a modest one, Hill's extension will end up having big implications on the next offseason.
The Diamondbacks won't be worrying about that, though, as they'll have a quality second baseman for the next three seasons to hit in the middle of their lineup.