His great uncle Albert E. Herrnstein played for Fielding H. Yost's famed "Point-a-Minute" teams in 1901 and 1902.

[4] He rushed for 475 net yards on 123 carries, scored seven touchdowns and tied with Terry Barr as Michigan's leading scorer in 1956.

[1][3] In a preview of the 1957 season, The Sporting News called Herrnstein "Michigan's Big Gun" and a "pounding fullback.

[6] In the 1958 season opener, Herrnstein rushed for a career-high 144 yards and scored two touchdowns against the USC Trojans.

"[2] At the time, Herrnstein said, "I'll leave school at the end of the semester in January and plan to return in September to finish up.

He appeared in 105 games, compiling a .244 batting average with 21 doubles, three triples and 10 RBIs, as he helped lead the team to a 78–48 record.

[12] Herrnstein later recalled that he was disappointed with his offensive performance at Des Moines: "That first year I didn't think I'd ever hit.

He appeared in 159 games for the Lookouts and batted .292 with a .365 on-base percentage, 22 doubles, six triples, 17 home runs, and 95 RBIs.

He appeared in 148 games and compiled a .293 batting average, .356 on-base percentage, 30 doubles, seven triples, 23 RBIs, and six stolen bases.

[14] He made his major league debut on September 15, 1962, and over the next two weeks he appeared in eight games for the Phillies, all as a pinch hitter.

"[8] With Wes Covington, Tony González, and Johnny Callison entrenched in the outfield, the Phillies saw an opportunity for Herrnstein to become their starting first baseman, replacing Roy Sievers.

Accordingly, and after a brief stint with the Phillies at the start of the 1963 season, Herrnstein was optioned to the Little Rock Travelers to allow him to try his hand at first base.

[8] Herrnstein appeared in 124 games for Little Rock, batting .271 with a .361 on-base percentage, 19 doubles, 22 home runs, and 73 RBIs.

[15] On September 23, 1963, he hit his first major league home run off Don Larsen of the San Francisco Giants.

The blow, which flew over the right-center field fence at Candlestick Park,[8] gave the Phillies a 5–4 victory.

In his next game, he hit a two-run, game-winning double down the left field line off Pittsburgh Pirates pitcher, Roy Face.

Traded along with him was 23-year-old Ferguson Jenkins – later to be inducted into the Baseball Hall of Fame – but then a prospect who had (to that point) only appeared in eight big league games.

[15] Only one month later (in late May), Herrnstein was traded to the Atlanta Braves in exchange for first baseman Marty Keough.

[12] In December 1966, Herrnstein was traded by the Braves with Chris Cannizzaro to the Boston Red Sox in exchange for Julio Navarro and Ed Rakow.