
Year Team Lg Age Lvl AB XBH BB AVG/OBP/SLG ----------------------------------------------------------- 1968 Marion App 18 Rk 234 20 -- 321/---/419 1969 Visalia Calif 19 A+ 393 39 -- 326/---/511 1969 Pom. Beach FSL 19 A+ 65 8 -- 354/---/600 1970 Memphis Tex 20 AA 461 47 -- 297/---/503 1971 Tidewater IL 21 AAA 497 51 -- 290/---/479Milner spent one season apiece at Double-A Memphis and Triple-A Tidewater, hitting for solid average and power at both stops, before getting called up to the Mets for a cup of coffee at the end of the 1971 season. He made his big league debut on September 15, 1971, grounding out as a pinch hitter in a 6-2 loss to the Cubs. He appeared in nine games over the final two weeks of the season, collecting two hits in eighteen at-bats, mostly as a pinch hitter.
Milner reported to spring training with the Mets in 1972 and was named "rookie of the spring" after hitting .296 with three homeruns and 11 RBI. He began the season in a part-time role and was booed mercilessly by the Shea faithful each time he appeared as a pinch hitter in lieu of Willie Mays. Milner took over in left field on a fairly-regular basis in the middle of May and finished the season batting .238/.340/.423. The average wasn't great, but he showed good discipline at the plate and whacked 17 homeruns en route to a third-place finish in the Rookie of the Year voting (teammate John Matlack won the award).
Year Age PA XBH BB AVG/OBP/SLG EQA WARP3 VORP -------------------------------------------------------- 1971 21 18 1 0 167/167/222 .105 0.1 -1.9 1972 22 423 31 51 238/340/423 .287 3.8 10.6 1973 23 519 38 62 239/329/432 .279 2.7 12.7 1974 24 576 39 66 252/337/408 .279 4.9 19.0 1975 25 255 18 33 191/302/336 .243 1.2 -5.1 1976 26 511 44 65 271/362/447 .298 5.4 21.9 1977 27 453 35 61 255/353/415 .282 4.1 13.4

The Mets went all the way to the World Series in 1973, and Milner certainly played a part in their amazin' run. He didn't pick up a single extra-base hit in the NLCS against the Reds or in the World Series against the Athletics, but he collected eleven singles and drew ten walks to bat .250 and post an on-base percentage of .389.
Milner returned to first base in 1974 and spent the whole season there, clubbing 20 homeruns and showing good patience at the plate. The Mets followed up their World Series run by losing 90 games in 1974, including a ">4-3 loss to the Cardinals on September 11 that lasted more than seven hours and in which Milner -- and eight other ballplayers -- played all 25 innings.
Milner got off to a rough start in 1975, finishing April hitting just .167/.333/.278. He had battled shin splints and a bruised right hand during spring training and spent the majority of the season just trying to find his groove. He appeared in only 91 games that year, batting a paltry .191/.302/.336, and relinquishing regular outfield duties to Rusty Staub, Del Unser and Dave Kingman, while Mets Kranepool took the majority of the starts at first base. It was a season Milner would just as soon forget, and he did just that at the start of the 1976 season, hitting .500/.589/.795 through his first fourteen games.
Milner's season hit a bump at the end of April when he pulled a thigh muscle that would cost him twelve games. He went on to have the best season of his career, though he hit just .248/.336/.413 after returning from the injury. He returned in 1977 for his sixth -- and final -- season with the Mets, hitting .255/.353/.415 for yet another lousy Mets team. Following the season, Milner was dealt to the Pittsburgh Pirates in a four team, eleven player trade that also involved the Rangers and the Braves that netted the Mets outfielders Willie Montanez and Tom Grieve (father of future big leaguer Ben Grieve) and Ken Henderson. The deal also cost the Mets Matlack, who would have his best season as a pro the following year in Texas.
Tragically, Milner died of cancer in 2000 near his home in Atlanta, GA, at the far-too-young age of 50. He led the Mets in homeruns during his first three full seasons, and led the team in OPS in 1976 with a mark of .809, 36% better than the league. He had some pop in his bat and he knew how to take a walk, and he was a fine hitter in five of his six seasons at Shea.
Sources
John Milner at Baseball-Reference.com
John Milner at Baseball Prospectus
John Milner at The Baseball Cube