Messersmith is most famous for his role in the historic Seitz decision which led to the downfall of Major League Baseball's reserve clause and ushered in the current era of free agency. It began when Messersmith went to spring training in 1975 and began negotiating his 1975 contract. He asked for a no-trade clause which the Dodgers refused. According to author John Helyar, in The Lords of the Realm, Messersmith was also deeply offended by general manager Al Campanis "inject(ing) a personal issue" into the talks (it "cut so deeply with him," Helyar has written, that Messersmith since has never been able to bring himself to disclose or discuss it), and the pitcher refused to deal with anyone lower than team president Peter O'Malley.
He also pitched 1975 without a contract, leading the National League in complete games and shutouts and finishing second in earned run average with 2.29, not to mention winning a Gold Glove (his second) as the league's best-fielding pitcher. Messersmith and Dave McNally were the only two players in 1975 playing on the one year reserve clause in effect at the time, technically; McNally's season ended early due to injuries and he returned home, intending to retire, but agreeing to players' union director Marvin Miller's request that he sign onto the Messersmith grievance in case Messersmith ended up signing a new deal with the Dodgers before the season ended.
"It was less of an economic issue at the time than a fight for the right to have control over your own destiny," Messersmith told The Sporting News, looking back on his decision a decade later. "It was a matter of being tired of going in to negotiate a contract and hearing the owners say, 'OK, here's what you're getting. Tough luck'."
Messersmith and McNally won their case before arbitrator Peter Seitz, who was fired by the owners the day afterward. McNally followed through on his intention to retire but Messersmith signed a three-year, $1 million deal with the Atlanta Braves. Among other things, then-Braves owner Ted Turner suggested the nickname "Channel" for Messersmith and jersey number 17, in order to promote the television station that aired Braves games. Major League Baseball quickly nixed the idea.
Messersmith struggled trying to live up to his new contract and was sold to the New York Yankees after the 1977 season, having gone 16-15 in two seasons with the Braves, the second marred by injuries. He had further injury trouble with the Yankees---and ran into disaster with injuries. The Yankees released him after the 1978 season and he signed, ironically, with the Dodgers. Ironically again, when the Dodgers signed him for that final go-round, they gave him the very thing their first refusal drove him toward testing and defeating the old reserve system: a no-trade clause. But the injuries and stress as the reserve clause's conqueror had taken too much toll; Messersmith pitched in only 11 games for the 1979 Dodgers, going 2-4 with a 4.90 ERA, and retired after the Dodgers released him.