Any executive will tell you that free agency is an inexact science, but the Red Sox have hit on quite a few signings that have been catalysts to World Series rings. 

From Manny Ramirez in 2000 to J.D. Martinez this offseason, here are the 10 best free agent signings the Sox have made this century: 

10. John Lackey

Five years, $82.5 million

The best free agent pitcher on the market ahead of the 2010 season, Lackey really didn’t live up to the big-money deal he landed — 47-43, 4.46 ERA in Boston — but did elevate his game en route to a 2013 World Series.

Lackey delivered a dominant start against the Tigers in the ‘13 ALCS, and picked up the win in Boston’s championship clincher against the Cardinals. The epicenter of the chicken and beer controversy in 2011, he was able to turn it around and get a standing ovation from Fenway Park as he walked off the mound in Game 6.

He was traded for World Series hero Joe Kelly, so Lackey gets bonus points for that, too. 

9. Adrian Beltre

One year, $9 million

One of the biggest Red Sox blunders of the 21st century was letting Beltre walk after one season.

The future Hall of Famer was outstanding in 2010, hitting .321 with 28 homers, 49 doubles and 102 RBIs, but the Red Sox opted to spend money — that could have re-signed Beltre — on Adrian Gonzalez instead. Third base became something of a black hole, with a past-his-prime Kevin Youkillis, Will Middlebrooks, and eventually, Pablo Sandoval manning the hot corner. Beltre was voted to three more All-Star Games as a Ranger.

8. David Price

Seven years, $217 million

Now that he’s opted in Price has plenty of time to move up and down this list, but as it stands he sits eighth. 

The Red Sox made Price the richest pitcher in baseball history in December of 2015, and there have been some serious highs and lows in his first three years. After a very good but not great 2016 ended with a playoff meltdown, Price turned in a 2017 to forget. His berating of Dennis Ecklersley was a rock-bottom moment for an underachieving team. 

But Price’s redemption tour last season was incredible. Building off a solid first half, Price was one of the best pitchers in baseball after the All-Star break. He picked up his first playoff win as a starter against the Astros in the ALCS, and then the training wheels came flying off. Price put the Red Sox on his back in the World Series — he should have been MVP — delivering an absolutely brilliant Game 5 clincher. 

7. Bill Mueller

Three years, $6.7 million

One of the under-the-radar ‘04 “idiots,” Mueller may be the best value signing the Sox have ever made. 

The heady third baseman won a batting title from the No. 8 hole, became the first player in history to hit grand slams from both side of the plate in the same game, and singled Dave Roberts home after the stolen base heard ‘round the world in Game 4 of the ‘04 ALCS. 

The last part shouldn’t come as too big a surprise though; Mueller batted .455 against Mariano Rivera, a future first-ballot Hall of Famer.   

6. Johnny Damon

Four years, $31 million

Clad in shoulder-length hair and a beard, Damon was the poster child for that team of idiots, and came to Boston as advertised. 

The speedy center fielder led off and set the tone, named to two All-Star teams during his four seasons with the Sox. Damon was terrific in 2004, batting .304 with 20 home runs and 94 RBIs, and going deep twice in the Game 7 clincher against the Yankees. 

Of course, Damon was vilified for leaving Boston for more money in New York, but this list is about the good times. 

5. Keith Foulke

Three years, $18.75 million

After a soul-crushing ALCS loss to the Yankees in ‘03, the Red Sox had a ton of talent but were just a piece or two away from putting it all together. 

Enter Keith Foulke (and Curt Schilling). 

The closer left it all on the mound to help Boston break The Babe’s curse. As their epic ALCS comeback was unfolding, Foulke took the ball five games in a row — at one point throwing more than 100 pitches in three days — and didn’t allow a run; his postseason was other-worldly. 

Foulke wasn’t the same the next two years, but the legend was written in ‘04. 

4. Koji Uehara

One year, $4.75 million

Uehara closing wasn’t Plan A (Joel Hanrahan) or Plan B (Andrew Bailey) in 2013, but Plan C was darn near automatic when he got his shot.

Ben Cherington took a flyer on the 38-year-old former Japanese Leaguer, and Uehara was lights out. He posted a 1.09 ERA in ‘13 and his 0.565 WHIP was the best ever for a reliever with at least 50 innings. Uehara allowed one run the entire postseason and was named the ALCS MVP. 

That dominance continued until he passed the baton to Craig Kimbrel in 2016.

3. J.D. Martinez

Five years, $110 million

Alex Cora has gotten a ton of credit for changing the culture — and deservedly so — but nobody had a bigger impact on the ‘18 Red Sox than J.D. Martinez. 

Mookie Betts was the MVP of the league, but Martinez was the MVP of the team. 

Martinez’s obsession with hitting was contagious in the clubhouse, and the best bat on the market somehow exceeded the colossal expectations facing him in Boston.

A triple crown threat, Martinez batted .330 with 45 homers and 130 RBIs. He was so good that he earned the No. 3 spot on this list after one season. 

2. Manny Ramirez

Eight years, $160 million 

Agreeing to terms with Ramirez didn’t just land the Red Sox one of the best right-handed hitters to ever play the game. It also signaled to the league that there were willing to spend — really spend — on free agents that were worth it. 

Ramirez certainly came with his, uh, idiosyncrasies, but during eight seasons in Boston he hit .312 with 274 homers and a .999 OPS. He and David Ortiz formed a lethal 3-4 combination in the middle of the Red Sox lineup, and Ramirez picked up two rings during his time in Boston. 

1. David Ortiz

One year, $1.25 million

Do we even need to explain this one? 

Ortiz is the most important player in Red Sox history. Period. 

Chris Mason is a Red Sox beat writer for the Daily News and CNHI Sports Boston. Email him at cmason@newburyportnews.com, and follow him on Twitter at @ByChrisMason.