BOSTON – He swatted 41 home runs in 1970 and the Minnesota Twins rewarded Harmon Killebrew with a $115,000 salary the next season, making him one of the highest paid players, at the age of 35.

Killebrew hit 28 home runs that year, and then 26 homers in 1972.

But at age 37, and still drawing six-figure salaries, Killebrew hit only five home runs after a knee injury limited him to 69 games.

He played 122 games at the age of 38, but hit only 13 home runs.

Age caught up with Killer.

We bring you this moment in history because another slugger will be turning 37 in the offseason.

How effective will Big Papi be next year?

David Ortiz will be a free agent after this season, just like last year.

And, like last year, the Boston Red Sox need to examine their options with Ortiz.

Boston could:

1. Not offer Ortiz a new contract (doubtful).

2. Offer a one-year contract at much less than the $14.575 million he made this year (unlikely).

3. Repeat last year’s scenario of offering him arbitration and then signing him to a one-year deal, which will guarantee him a raise over last season (possible).

4. Give Ortiz the security he wants with at least a two-year deal, but at less money per season (also possible).

Any contract is a gamble, given Ortiz’s age. Ortiz began this season in excellent shape and led the team in home runs (23) until a strained Achilles tendon shut him down. He’s played only 90 games, meaning he’ll miss 44 percent of the season.

But Boston needs Ortiz, especially after trading Adrian Gonzalez. The Red Sox don’t have another proven power hitter.

Jarrod Saltalamacchia (24 home runs through 107 games) is having a breakout year, at least in terms of power. Cody Ross (21 homers, 112 games) is a good fit at Fenway, and Will Middlebrooks (15 homers, 75 games) will only get better.

But for a big bat in the middle of the lineup, Boston needs to have Ortiz strolling to the plate, spitting into his gloves, clapping his hands, and then stepping into the box.

The concern remains his age and what has happened to other sluggers like Harmon Killebrew.

Manny Ramirez, Ortiz’s former companion in the Sox lineup, saw his numbers drop. He hit a total of 39 home runs for the Red Sox and Dodgers at age 36 in 2008. His home runs and games played declined after that, 19 in 104 games at age 37, 16 in 90 games at 38.

Reggie Jackson went from 39 home runs at age 36 to 14 home runs (116 games) the next year. He rebounded with 25 home runs at age 38.

But decline is not automatic at Ortiz’s age. Others hitters saw little change, if not an increase in power as they got older.

Hank Aaron hit 47 home runs and Babe Ruth hit 41 at age 37. Jim Thome hit 35 at age 36, then 34 the next year.

Barry Bonds hit 73 home runs at age 36, then 46 and 45 the next two years. (Of course, an asterisk next to those numbers may be warranted.)

As for Ortiz, questions about a decline in performance began in 2008 when he was hitting .193 through May 2 and struggled against left-handers. Then he injured his wrist at the end of the month.

Ortiz returned to hit .264 with 23 home runs in 109 games. In 2009, Ortiz hit .238 with 28 home runs.

Ortiz ended the decline in 2010 (.270, 32 home runs) and was solid again in 2011 (.309, 29 homers).

That Ortiz continues to work on his game is obvious. He has made adjustments against left-handed pitching. In 2011 he hit .329 with eight homers against left-handers; this year he was .320 with nine homers in 125 at-bats vs. lefties.

Ortiz was the team’s only All-Star this year. But then he injured his Achilles tendon July 16 while running the bases. He returned Aug. 24, but it was only for one game.

While frustrated by the injury, Ortiz feels confident he will be back in good shape.

“In the offseason, I’ll be fine,” he said last week. “I’ll just go back to normal.”

Assuming he is re-signed, expect a “normal” Ortiz to arrive in Fort Myers, Fla., next February in solid shape, ready to show what his 37-year-old body will do.

If his body does not betray him, Ortiz seems capable of putting up big numbers again.

Staff Writer Kevin Thomas can be reached at 791-6411 or:

[email protected]

Twitter: ClearTheBases