There’s a mound of difference: How pitching has changed in the last 50 years

Phil Regan’s return last week to Wrigley Field as the interim pitching coach of the Mets not only provided a link to the 1969 Cubs but to a era when pitching staffs were used far differently than they are now.

Regan pitched for the Cubs in 1968-72 and was their bullpen ace for the first three of those seasons. And the term was ‘‘bullpen ace,’’ not ‘‘closer.’’ Closers didn’t come into vogue until the late 1970s, when the Yankees with Goose Gossage and the Cubs with Bruce Sutter pioneered the practice of saving the best reliever to finish close games.

By the numbers, today’s game and Regan’s game are completely different baseball worlds.

• Regan led the majors with a career-high 25 saves in 1968. Seventeen pitchers had at least 25 saves last season, led by the Mariners’ Edwin Diaz with 57.

• Bullpen aces were expected to enter games earlier than closers and pitch multiple innings.

In 1968, Regan appeared in 73 games and pitched 134‰ innings. He entered one game in the fourth inning and appeared in the seventh or earlier 21 times. Last season, Diaz also appeared in 73 games but pitched only 73„ innings. He never appeared earlier than the eighth, and he did that only three times.

For the 1969 Cubs, who famously faded while the Mets surged to first place, Regan saved 17 games in 71 appearances and pitched 112 innings. That gave him back-to-back seasons with more than 100 innings in relief. The leader in relief innings last season was the Athletics’ Blake Treinen with 80„.

• Although closers pitch fewer innings than old-style bullpen aces did, relief staffs pitch much more.

Last season, 40.1 percent of innings were pitched by relievers. In 1968, relievers pitched only 26.1 percent of innings.

In 2018, 238 pitchers — nearly eight per team — made at least 30 relief appearances. Fifty years earlier, with 20 teams in the majors instead of 30, only 66 pitchers — just more than three per team — made at least 30 relief appearances.

• Starting pitchers carry much less of the burden than in Regan’s time. In 1968, there were 897 complete games, nearly 45 per team. A year later, with conditions less friendly to pitchers, starters completed 982 games, about 49 per team. Fast-forward to 2018, and the 30 teams combined for only 42 complete games.

In 1968, when Regan had his best season, he finished 62 games, not far off Diaz’s 65 last season. Overall, however, the top 20 in saves that season closed 23.08 percent of games (750 of 3,250), while starters finished 27.60 percent. In 2018, starters finished only 0.86 percent of games. The top 30 saves men — expanded to account for the increased number of teams — closed 25.71 percent (1,250 of 4,862).

Bullpen aces in Regan’s time finished fewer games than starters, but closers today finish about 30 times as many games as starters. That’s a huge gap, with Regan present at both ends.