And he will be a member of the Angels through the year 2021, which is so far in the future that you have to put "the year" in front of it; it's only 42 years before Zefram Cochrane will invent the warp drive, for example.
Craig Calcaterra of Hardball Talk posits that in the last few years of this deal, the Angels will regret it, because, well:
Name one player who remained elite in his age 36-41 seasons. Now name one not named Barry Bonds. Yeah, it’s fairly obvious that El Hombre — can we still call him that? — will be overpaid, perhaps severely so, for the second half of this deal.
Let's leave Barry Bonds out of this conversation, for any one of a number of reasons. What Craig is forgetting, I think, is that Pujols isn't, for example, Alfonso Soriano, whose eight-year deal (that still has three years to run) has installed him as Cubs fans' favorite whipping boy.
Instead, Pujols is a first-ballot Hall of Famer who might end his career as the greatest righthanded hitter in the history of the game. If he never played another game, he'd still be a first-ballot Hall of Famer off his performance to date.
Further, not only can I name one player who remained elite in his age 36-41 seasons, I can name five, in more or less chronological order:
Ty Cobb: Cobb hit .346/.424/.485 in his age 36-41 seasons; one year before that he hit .401. He was still good for about 17 SB a year, even at that age and even in an era where the stolen base was being de-emphasized. Cobb, never a power hitter, even bowed to that era: he had his career high in home runs (12) at age 38 in 1925.
Babe Ruth: didn't play until age 41, but even including his poor .181 career sendoff with the Boston Braves in 1935, from age 36-40 Ruth hit .324/.466/.620 with 149 HR and 499 RBI. He led the AL in HR once, in SLG once, and in OBA twice in that span. The Yankees won 91 or more games all four years before Ruth left for Boston, and won the 1932 pennant with 107 victories.
Ted Williams: The Splendid Splinter hit .336/.470/.623 from age 36-41, including a spectacular 1957 season when he led the AL in BA (.388), OBP (.526), SLG (.731), OPS (1.257) and had an adjusted OPS+ of 233, ninth-highest all-time. He also hit .316 at age 41 in 1960 and homered in his final big-league at-bat.
Stan Musial: Stan the Man, who will now likely forever remain the greatest Cardinals player ever, hit .311/.396/.516 during these six seasons, hitting .330 or better in three of them, including the last, at age 41. At age 36 in 1957, he led the NL in BA (.351), OBP (.422) and OPS (1.034), losing the MVP award by just nine points to the man below (who was 13 years younger and on a pennant-winner).
Henry Aaron: The only righthanded hitter on this list, Hammerin' Hank hit .283/.378/.543 in his age 36-41 seasons -- and also averaged 38 home runs and 108 RBI over those five years, during which he set his career high in homers, 47 in 1971 at age 37, when he also led the NL in SLG (.669) and OPS (1.079) and had a 194 OPS+.
These are the players Pujols should be compared to, because by the time he's done, barring injury, he should put up numbers that will be among the all-time leaderboards in hits, runs, RBI, walks and home runs. I don't see any reason why Pujols can't match the production of those five players, all first-tier Hall of Famers (which Pujols will be when he's eligible), when he's in his late 30s.
The real change comes in this stat: playing time. The performances were stellar, but with more rest (or, time missed with injuries). Cobb averaged 121 games per year during that stretch; Ruth, 114; Williams, 118; Musial, 126 and Aaron 131. All but Aaron played the vast bulk of their careers during the time of the 154-game schedule, so adjust any Pujols estimate you extrapolate from that upward by about 5%. Pujols has averaged 155 games per season in his career to date; even lopping off 25% of those games, you still have an All-Star caliber hitter.
Conclusion: Pujols should be able to continue to play at a high level until the end of this contract, just with somewhat lower playing time. If the Angels can win a World Series or two before then, I think they can live with that.