It's one of the most lopsided trades in MLB history, and it happened 50 years ago Friday.

On Dec. 10, 1971, the Mets traded Nolan Ryan (plus Leroy Stanton, Don Rose and Frank Estrada) to the Angels for Jim Fregosi.

At the time, the trade seemed fair for both sides. The Mets got an All-Star infielder, addressing a major area of need. The Angels got a promising but erratic arm who had yet to realize his potential in five seasons with New York. The reaction to the Ryan trade was nothing like the Midnight Massacre six years later, when the Mets traded away Tom Seaver.

Of course, the way it turned out, "What if Nolan Ryan stayed with the Mets?" is one of the biggest what-ifs in New York sports history. Ryan became baseball's strikeout king, a 300-game winner and a Hall of Famer. Fregosi didn't last even two seasons in New York.

Here's a look back at the trade, its legacy and Ryan's historic career afterward.

Why the Mets traded Ryan

• Ryan was wild.

The lead of The New York Times' story on the trade sums it up: "The Mets finally gave up on Nolan Ryan's wandering fastball today."

The 24-year-old fireballer was an electric talent, but he had big control issues. In 1971, his last season with the Mets, Ryan went 10-14 with a 3.97 ERA … and he issued 116 walks with his 137 strikeouts. Since his big league debut in 1966, Ryan had walked 6.1 batters per nine innings, versus 8.7 strikeouts per nine innings.

That's why the Mets were willing to give him up. After the trade, Mets general manager Bob Scheffing said, "I really can't say I quit on him. But we've had him three full years and, although he's a hell of a prospect, he hasn't done it for us. How long can you wait? I can't rate him in the same category with Tom Seaver, Jerry Koosman or Gary Gentry."

• Fregosi was an All-Star.

Fregosi was an established All-Star, and in his prime at age 29, when the Mets traded for him. Though he had struggled through injury in 1971, he was only one year removed from a string of five consecutive All-Star seasons with the Angels from 1966-70, and he had received MVP votes in eight straight seasons from 1963-70.

Over those eight seasons, Fregosi was a .271 hitter who averaged 13 home runs and 61 RBIs a year while posting a 119 OPS+, meaning he was nearly 20% better than a league-average hitter over that time.

• The Mets needed a third baseman.

The Mets hoped Fregosi would be their solution at the hot corner. In the early years of their franchise, they were a long way away from finding their Howard Johnsons or David Wrights.

Though Fregosi was a shortstop with the Angels, shortstop to third base is a normal move, and more importantly, Fregosi had averaged 157 games per season from 1963-70 to go along with his offensive production.

The Mets, meanwhile, had used 45 different third basemen in their 10 seasons, and were deploying a combination of Wayne Garrett and Bob Aspromonte when they traded for Fregosi. In 1971, Aspromonte batted just .225 with five home runs and a 68 OPS+ in 104 games; he never played in the Majors again after that season. Garrett, who was the regular third baseman but missed most of the '71 season for military service, batted .213 with one home run and a 59 OPS+ in the 56 games he did play.

• The Mets had a win-now philosophy.

Two years after the 1969 Miracle Mets won the franchise its first World Series championship, the Mets were looking for players who could help them do it again.

They'd missed the playoffs in 1970 and '71, but finished with a winning record both years, and manager Gil Hodges in particular thought Fregosi, not Ryan, was the type of player who could help the Mets make an immediate postseason run.

"You always hate to give up on an arm like Ryan's," Hodges said after the trade. "He could put things together overnight, but he hasn't done it for us and the Angels wanted him. I would not hesitate making a trade for somebody who might help us right now, and Fregosi is such a guy."

Ryan, on the other hand, didn't really have a spot in the Mets' playoff rotation. He'd helped out of the bullpen during the '69 championship run, but teams used three-man starting rotations in the playoffs back then, and New York had a star trio of Seaver, Koosman and Gentry already in place. They started all eight of the Mets' postseason games in '69, and 11 of the 12 games during New York's next pennant run four years later in 1973. Where would Ryan have fit in?

The trade's legacy

In hindsight, Angels GM Harry Dalton is the one who had it right when he bet on Ryan's talent.

"We picked up one of baseball's best arms in Ryan," he said after the trade. "We know of his control problems, but he had the best arm in the National League and, at 24, he is just coming into his own."

Ryan took his overpowering fastball to the American League and became an instant star. In his first year with the Angels in 1972, he made 39 starts, went 19-16 with a 2.28 ERA in 284 innings and led the Major Leagues with 329 strikeouts, a 10.4 K/9 and nine shutouts.

The control issues didn't vanish -- Ryan also led the Majors with 157 walks and 18 wild pitches -- but it didn't matter so much when he was striking out the world. Ryan was an All-Star for the first time in his career, finished eighth in AL Cy Young Award voting and got some MVP votes.

Ryan would go on to be a five-time All-Star in eight seasons with the Angels. He finished in the top three of Cy Young Award voting three times and got MVP votes four times. He threw four of his record seven no-hitters. He became the instant ace of the Angels' rotation and led them to their first-ever playoff appearance as the AL West champions in his final year in California, 1979. Ryan was a franchise player.

As for Fregosi? He never got off the ground in New York. He played only 146 total games for the Mets in 1972 and '73 before they shipped him to the Rangers halfway through the '73 season for a player to be named later -- just to make room for catcher Jerry Grote's return from the disabled list.

Fregosi batted just .233 with five total home runs and an 85 OPS+ in his time in New York. He battled injuries throughout his tenure, including a broken thumb in his debut season in 1972.

When the Mets traded him away, Fregosi said, "Oh, I'm happy. It didn't look like I'd play here any more. I'm at the age I have got to play. I haven't played here really."

The Mets finished 83-73 but missed the playoffs with Fregosi as their regular third baseman in 1972. And they were in last place when they dealt him to Texas in July 1973. But they pulled off an amazing comeback down the stretch -- the "Ya Gotta Believe!" Mets went from last to first in the final month of the season, won the National League East, beat the Big Red Machine in the playoffs to win the pennant and pushed the A's to Game 7 of the World Series.

But New York never had a true star third baseman until HoJo took over the position in the mid-1980s. And a franchise defined by its great pitchers, like Seaver and Dwight Gooden, had to watch Ryan become one of the all-time greats with other teams.

Ryan's career after New York

Ryan's career numbers are historic: 324 wins, 5,714 strikeouts, seven no-hitters, two ERA titles, 11 strikeout crowns, six 300-K seasons.

His move to the Angels jump-started those numbers (though the only World Series ring he ever won was with the Mets). Here are some of the highlights of Ryan's Angels tenure from 1972-79.

• Ryan won 138 games with the Angels and totaled 2,416 strikeouts -- averaging an incredible 302 strikeouts a year.

• He led the American League in strikeouts in seven out of his eight seasons with California, and led the Majors in five of those seasons.

• He set the Modern Era record for strikeouts in a single season with 383 in 1973, breaking Sandy Koufax's mark of 382 set in 1965.

• He struck out more than 300 batters five times in those eight seasons. That's more 300-K seasons than any pitcher but Randy Johnson has for their career (Johnson and Ryan are tied with six each).

• He pitched 40 shutouts for the Angels, leading the Majors in shutouts three times (nine in 1972, seven in '76 and five in '79).

• He threw four no-hitters as an Angel -- against the Royals on May 15, 1973; against the Tigers on July 15, 1973; against the Twins on Sept. 28, 1974, and against the Orioles on June 1, 1975. Koufax is the only other pitcher in history with four career no-hitters -- and Ryan went on to throw three more, one with the Astros and two with the Rangers.

• He struck out 19 batters in a nine-inning game on Aug. 12, 1974, against the Red Sox, which at the time tied the MLB record for most K's in a nine-inning game. He also struck out 17 in his second no-hitter, which set a record for most K's in a no-hitter.