Adrian Beltre announced his retirement after last season, closing the door on a career that could lead him to Cooperstown.

Beltre built his excellent resume over 21 seasons in the Majors, but arguably, his two best years (2004 and '10) had something in common. Both were "walk years," meaning they came right before Beltre reached free agency.

The idea that players always step up their games in such situations, with a big contract acting as motivation, is far from the truth. Plenty flop, or simply perform near their career norms.

But there is a long history of exceptional walk years as well, and Beltre is a big part of it. Here is a look at 20 of the best.

1. Alex Rodriguez, 2000 Mariners
Stats: .316/.420/.606 (163 OPS+), 41 home runs
Contract: 10 years, $252 million with Rangers
A-Rod only turned 25 in the middle of the 2000 season, when he racked up more than 10 Wins Above Replacement (WAR), per Baseball-Reference. The resulting deal with Texas smashed records and remains one of the biggest in baseball history.

2. Barry Bonds, 1992 Pirates
Stats: .311/.456/.624 (204 OPS+), 39 stolen bases
Contract: Six years, $43.75 million with Giants
Bonds entered the market coming off his second 30-30 season and National League Most Valuable Player Award in three years, as well as his third straight Gold Glove Award. He was even better in his first season in the Bay Area, taking MVP honors yet again.

3. Adrian Beltre, 2004 Dodgers
Stats: .334/.388/.629 (163 OPS+), 48 home runs
Contract: Five years, $64 million with Mariners
Only Bonds prevented Beltre from being NL MVP, as the 25-year-old authored a breakout campaign at the perfect time. Beltre's 9.6 WAR remains the most by a third baseman since Mike Schmidt in 1974.

4. Alex Rodriguez, 2007 Yankees
Stats: .314/.422/.645 (176 OPS+), 54 home runs
Contract: 10 years, $275 million with Yankees
A-Rod broke his own record for total dollars after opting out of the original deal. He was coming off his third American League MVP Award in five years and had led the AL in runs, homers, RBIs, slugging and OPS.

5. Zack Greinke, 2015 Dodgers
Stats: 19-3, 1.66 ERA (222 ERA+)
Contract: Six years, $206.5 million with D-backs
The right-hander's ERA was the lowest by a qualified pitcher since Greg Maddux in 1995, and he put together a 45 2/3-inning scoreless streak in June and July that was the longest in the Majors since Orel Hershiser set the record of 59 in 1988.

6. Greg Maddux, 1992 Cubs
Stats: 20-11, 2.18 ERA (166 ERA+)
Contract: Five years, $28 million with Braves
Maddux won his first NL Cy Young Award in 1992, when he allowed only seven homers in 268 innings. But he became a pitching legend in Atlanta, where he extended his Cy Young streak to four.

7. Jason Giambi, 2001 A's
Stats:.342/.477/.660 (199 OPS+), 38 home runs
Contract: Seven years, $120 million with Yankees
Only the arrival of Ichiro deprived Giambi of a second straight AL MVP Award, though he was even better than in 2000. The lefty slugger is the only AL first baseman since Rod Carew in 1977 to reach the 9-WAR mark in a season.

8. Jim Thome, 2002 Indians
Stats: .304/.445/.677 (197 OPS+), 52 home runs
Contract: Six years, $85 million with Phillies
The 2002 season was arguably the best of a 22-year career that landed Thome in the Hall of Fame on the first ballot in 2018. It was his lone 50-homer campaign, on his way to 612 total.

9. Catfish Hunter, 1974 A's
Stats: 25-12, 2.49 ERA (134 ERA+)
Contract: Five years, $3.75 million with Yankees
This was not the typical "walk year" we think of today. Hunter signed a two-year contract going into 1974, when he took AL Cy Young honors, and Oakland won its third straight World Series championship. But A's owner Charlie Finley was found to not be honoring the terms of Hunter's deal, and the star pitcher was declared a free agent -- setting off the first of many offseason baseball bidding wars. (Two years later, the reserve clause was history, and the true free-agent era began).

10. Carlos Beltran, 2004 Royals/Astros
Stats: .267/.367/.548 (133 OPS+), 42 stolen bases
Contract: Seven years, $119 million with Mets
It wasn't so much what Beltran did in the regular season that vaults him this high, though he did come within two homers of a 40-40 campaign. Rather, it's his memorable postseason run with Houston, when he hit .435/.536/1.022, with a record-tying eight homers over 12 games.

11. Rickey Henderson, 1989 Yankees/A's
Stats: .274/.411/.399 (132 OPS+), 77 stolen bases
Contract: Four years, $12 million with A's
Oakland traded its superstar leadoff man to the Yankees after the 1984 season, then reacquired him in June 1989. He went 52-for-58 in steal attempts over 85 regular-season games, then hit .441/.568/.941 with 11 steals in the postseason, as the A's won the World Series.

12. Kevin Brown, 1998 Padres
Stats: 18-7, 2.38 ERA (164 ERA+)
Contract: Seven years, $105 million with Dodgers
After winning a ring with the 1997 Marlins, the right-hander was traded to San Diego and allowed only eight homers over 257 innings. He parlayed that into becoming MLB's first $100 million man.

13. J.D. Drew, 2004 Braves
Stats: .305/.436/.569 (157 OPS+), 31 home runs
Contract: Five years, $55 million with Dodgers
This was the first time the 28-year-old Drew was healthy enough to accrue at least 500 plate appearances, and he showed the talent that made him a top-five pick in both the 1997 and '98 Drafts.

14. Mark Teixeira, 2008 Braves/Angels
Stats: .308/.410/.552 (152 OPS+), 33 home runs
Contract: 8 years, $180M with Yankees
Tex was good for the Braves, and then even better after a non-waiver Trade Deadline deal, posting a 1.081 OPS in 54 games for the AL West-winning Halos.

15. Robinson Cano, 2013 Yankees
Stats: .314/.383/.516 (147 OPS+), 27 home runs
Contract: 10 years, $240 million with Mariners
This was the capper to a four-year stretch in New York in which Cano won four Silver Slugger Awards and two Gold Gloves at second base, while leading MLB position players in WAR (30.1).

16. Adrian Beltre, 2010 Red Sox
Stats: .321/.365/.553 (141 OPS+), 28 home runs
Contract: Six years, $96 million with Rangers
A season at Fenway Park was exactly what Beltre needed to remind the baseball world that he was a star, following five years in Seattle's pitcher-friendly environment.

17. CC Sabathia, 2008 Indians/Brewers
Stats: 17-10, 2.70 ERA (156 ERA+)
Contract: Seven years, $161 million with Yankees
The 2007 AL Cy Young Award winner endured a rough April in '08, but was on a roll when the Brewers acquired him in early July. What followed was an all-time great stretch run in Milwaukee -- 11-2 with a 1.65 ERA and seven complete games in 17 starts.

18. Manny Ramirez, 2000 Indians
Stats: .351/.457/.697 (186 OPS+), 38 home runs
Contract: Eight years, $160 million with Red Sox
Manny's adventurous defense in the outfield held down his overall value (4.8 WAR) considerably, but you can't ignore what a terror he was with a bat in his hands.

19. Albert Belle, 1998 White Sox
Stats: .328/.399/.655 (172 OPS+), 49 home runs
Contract: Five years, $65 million with Orioles
A fearsome hitter, Belle slammed at least 48 homers for the third time in four years, drove in 152 runs and led the AL in OPS. But a degenerative hip condition ended his career after two years in Baltimore.

20. Alfonso Soriano, 2006 Nationals
Stats: .277/.351/.560 (135 OPS+), 46 home runs
Contract: Eight years, $136 million with Cubs
Traded from Texas to Washington at the end of 2005, Soriano put together the fourth -- and most recent -- 40-40 season in baseball history.