[11] In his rookie year for Boston, Lonborg had a 9–17 win loss record and 4.47 earned run average (ERA).

The Red Sox and Twins faced each other in the season's final series and entered the final day (October 1) tied for first place; the Tigers were half a game out of first and needed to sweep a doubleheader from the California Angels to force a playoff between the winner of the Red Sox–Twins game.

Lonborg outdueled Twins ace Dean Chance in that finale, while the Tigers defeated the Angels in the first game but lost the second, putting the Red Sox in the World Series for the first time since 1946.

[1] Called upon to pitch the seventh and deciding game with only two days rest, he lasted six innings, but allowed six earned runs in a 7–2 loss.

[17] Teammate Dan Osinski remembered, "Lonborg couldn't break a pane of glass in the bullpen when he was warming up.

"[18] Shortly after being fired by the Red Sox, pitching coach Sal Maglie also criticized Williams's handling of Lonborg.

[2][20] In December of 1967, Lonborg tore the ligaments in his left knee while skiing, and his pitching career thereafter was marked by many injuries.

[2] In both 1970 and 1971, he spent time with the Triple-A Louisville Colonels while trying to recover from his injuries and to regain his pitching form, and he finished the 1971 season with the Red Sox going 10–7, his best record since 1967.

[24] Lonborg was traded along with George Scott, Ken Brett, Billy Conigliaro, Joe Lahoud and Don Pavletich to the Milwaukee Brewers in a ten-player trade that also sent Tommy Harper, Marty Pattin, Lew Krausse and minor-league outfielder Pat Skrable to the Red Sox on October 10, 1971.

[24] With the Philadelphia Phillies needing to improve its pitching staff beyond Steve Carlton, a future hall of fame pitcher and 329 game winner,[27] both Lonborg and Brett were acquired along with Ken Sanders and Earl Stephenson from the Brewers for Don Money, John Vukovich and Bill Champion on October 31, 1972.

[24] After retiring, Lonborg attended the Tufts University School of Dental Medicine, and graduated in 1983 and began practicing.

[1] He is active in many nonprofit organizations, including Catholic Charities, Little League Baseball, and The Jimmy Fund,[1] as well as the Susan G. Komen foundation and those seeking to treat cystic fibrosis.