5 bullpen usage trends to know

Given baseball's unpredictable nature, there aren't many guarantees one can make about the 2017 season. But there is little doubt there will be many calls to the bullpen, if recent history is a guide.
The increasing emphasis on relievers has been readily apparent for years, especially during the last couple of postseasons. It's a trend that has implications for rotation usage, scoring, pace of game and other important issues.
Just how much have things changed? To find out, MLB.com went back over the last 50 seasons (1967-2016) and looked at how bullpen deployment has evolved during that time.
Out of that research, here are five reliever usage trends to know:
1. The amount of relief appearances continues to climb
Last season, relief pitchers were called upon a whopping 15,307 times, which works out to a record 3.15 appearances per team, per game. Usage has been steadily rising since 1978, when the average was less than half as big (1.40), and starters threw more than 12 times as many complete games. The average number of relief appearances first crossed the 2.0 mark in 1990 and kept right on going, as clubs used at least three relievers per game for the first time in 2015.

It should be noted that bullpens are worked especially hard after rosters expand on Sept. 1. Last season, teams used 3.63 relievers per game during that period, compared with 3.05 prior to September. Consider that all six times in MLB history that opposing teams have combined to send in at least 15 relievers in a nine-inning game, that game has been played after Sept. 1. Five of those six contests have come in the past two years, including an 11-8 Boston win at Toronto last Sept. 11 in which the Red Sox and Blue Jays deployed eight relievers apiece, to cover a total of 11 1/3 innings.
2. Long relievers are an endangered species
As the average relief outing dipped from 1.75 innings in 1978 to 1.04 innings in 2016, the role of the long reliever has shriveled. Yes, teams still occasionally ask a bullpen arm to eat innings when a starter is knocked out early or a game goes into extras, but extended relief appearances are far less common these days.
Only 329 times in 2016 did a reliever stay on the mound for three innings or longer, compared with a high of 1,164 such outings in 1982. These appearances went from accounting for more than 17 percent of all relief outings in '82, to less than 2 percent in 2010 -- hovering around that level ever since. This past season, the Brewers produced only one outing of that length -- Brent Suter threw exactly three innings on Aug. 27 -- despite their bullpen tying for 10th in the Majors in most innings thrown.
3. Multi-inning appearances are a rarity
Let's flash back 40 years. When the bullpen door opened in 1977, it was close to a coin flip as to whether the new reliever would stay in the game for at least six outs. Three seasons earlier, the Dodgers' Mike Marshall had set records by making 106 relief appearances, including 62 of the multi-inning variety, and throwing 208 1/3 innings in that role to take the NL Cy Young Award.
But the proportion of relief outings to last at least two innings dropped from 44.8 percent in '77 to 35.4 percent in '87, to 19.5 percent in '97 and down to a low of 9.8 percent in 2014 before ticking back up slightly in each of the past two years. In 1987, a total of 45 pitchers made 20 or more relief appearances of two-plus innings -- more than from 2003-16 combined. Last year three pitchers (Chris Devenski, Erasmo Ramírez and Vance Worley) tied for the MLB lead with exactly 20 such outings.

4. Three is now the preferred number of outs
The modern bullpen is defined by rigid roles, at least in the regular season, with pitchers often assigned to the seventh, eighth or ninth inning and not straying from that spot with great frequency. Perhaps that's why the three-out relief appearance has become so prevalent. In 2016, a record 51.4 percent of the time a reliever entered, he pitched exactly one inning. While that rate has hovered in that range throughout the current decade, three-out appearances accounted for less than one-quarter of the total as recently as 1987, hitting a low of 18.9 percent in '76.
5. Closers in particular have become pigeon-holed
The save became an official statistic in 1969, but it wasn't until much more recently that the role of closer came to be so strictly defined. In '84, the Royals' Dan Quisenberry set a record by recording 27 multi-inning saves (two fewer than all MLB pitchers combined for this past season). That year, there were more saves of the multi-inning variety than those that required three outs or fewer.
But by '88, the year Dennis Eckersley emerged as a closer in Oakland, that dynamic had flipped. In the narrow period between '87 and '97, the proportion of saves lasting no more than one inning soared from 40 percent to 79.6 percent. That number peaked at 93.9 percent in 2014, and although last year it was back to 91.3 percent, it's too early to say whether that decrease is a new trend or simply a blip.