David Ortiz is 100 percent sure he's retiring at the end of the season. That is, if someone doesn't blow him away with a $25-million offer he says is the magic number to keep him in the big leagues.

If someone were to convince him to stick around for one more year with that money, he might actually be worth it. The 40-year-old isn't looking like someone on his last legs during his swan song campaign. Rather, he's leading baseball in slugging percentage and OPS, and is on pace to finish with 106 RBIs, 33 home runs, and 82 runs scored, according to Baseball Prospectus' projections.

None of that even mentions his continued heroics for the surging Red Sox, including his remarkable three-hit performance Saturday, capped by his 600th career double - a walk-off double, no less.

Ortiz's farewell tour is already moving up the list of great final seasons, and he's not even halfway through yet. Here's a look at some other great farewell campaigns in baseball history.

Sandy Koufax

Before the 1966 season began, Koufax decided the upcoming campaign would be his last due to elbow troubles. Though he was barely able to pitch with his gifted left arm, Koufax went out and won the pitching Triple Crown - 27 wins, 1.73 ERA, 317 strikeouts - while starting 41 games, completing 27 of them, and throwing 323 innings in what remains one of the greatest seasons ever by a left-hander. And then, just like that at age 30, he was gone.

Lou Brock

After breaking Ty Cobb's stolen base record in 1977, Brock's numbers fell off. By 1978, he'd lost his job as the Cardinals left fielder, was battling injuries, and couldn't even crack the 20 stolen base mark. But he regained his form for one final run in 1979, hitting .304/.342/.398 with 21 stolen bases, and reached the 3,000 hit mark near the end of the season. His farewell campaign was capped off by being named National League Comeback Player of the Year.

Mariano Rivera

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The greatest closer ever wasn't about to be cut down by a torn ACL sustained while shagging flies in Kansas City. After rehabbing his injury, the classy Rivera returned for a farewell season in 2014 and was feted with gifts from opposing clubs at every ballpark he visited. He was also very productive, saving 44 games for the Yankees while striking out 54 and walking just nine, good enough to win the AL Comeback Player of the Year award. It was indeed a fitting end for one of baseball's greatest ambassadors on and off the field.

Ted Williams

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"Teddy Ballgame" was going to go out his way: Hitting. Williams won his last batting title in 1958, two years before his farewell tour, and he went back above .300 one last time to say goodbye in 1960. His .316/.451/.645 line over just 390 plate appearances at age 41 was impressive enough, but how about 29 home runs and 2.9 WAR to go with it? Ortiz could surpass Williams for the finest goodbye season in Red Sox history - and unlike the stoic Williams, Papi will probably tip his cap upon hitting his final homer at Fenway.

Mike Mussina

Talk about ending a career on your own terms. Mussina, one of the more underrated pitchers of the 1990s and early 2000s, finished up his 18-year career by winning 20 games for the first time - and reaching double-digit wins for a 17th consecutive year. He also threw 200 innings for the 11th time, won a Gold Glove, and finished sixth in AL Cy Young voting. He decided to leave on a high note and retire following this excellent campaign, becoming the first 20-game winner to walk away from baseball since Koufax.

Al Kaline

Here's a case that Ortiz can take inspiration from, even if Kaline's farewell numbers weren't as eye-popping. The Tigers legend played just 91 games in 1973, and his production was dropping fast. But he came back in 1974 at age 39, appearing strictly as a designated hitter in the position's second year of existence, and went out with a bang. Kaline slashed .262/.337/.389 over 147 games, saw his home run numbers spike, and made one final All-Star appearance. He also reached the 3,000 hit mark near the end of the season, putting a nice cap on his Hall of Fame career.

Barry Bonds

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Bonds was still at the top of his game during his final go-round in 2007. He led all of baseball in OBP (.480) and walks (132), as well as intentional walks (43) over 126 games. He was also still good at mashing baseballs over fences, hitting his final 28 home runs, and became baseball's home run king in the process. Despite all of that, he wasn't signed by anyone in the offseason.

(Videos courtesy: MLB.com)