Atop the hitting leaderboards this season, you’ll find an unexpected — yet familiar — name: 40-year-old David Ortiz leads baseball in Weighted Runs Created Plus, a full 12 points beyond wunderkind Mike Trout. Big Papi’s return to the ranks of the elite hitters corresponds with a de facto loosening of one of his least-favorite rules: a restriction on how much time batters can take to ready themselves for the next pitch. This season, the pace of play has begun to creep back toward 2014 levels, and older hitters such as Ortiz may be reaping the benefits.Just before the 2015 season, new MLB Commissioner Rob Manfred added new rules designed to speed up the game. And they worked: after the average game took an all-time high of 3 hours and 2 minutes the previous year, it fell by 6 minutes in 2015. Manfred’s tweaks had the desired effect, and his attention moved to other problems in the game, like the lack of offense.But unlike offense, which continues to spike, Manfred’s pace-of-play fixes didn’t last long. The average game has nearly reverted to its 2014 high this year, at an even 3 hours. Part of that increase is due to the surge in offense — it takes longer to get 27 outs when outs are happening less frequently — but some of it comes from a decrease in pace, or the time between successive pitches. On average, the time between pitches has increased by 0.07 seconds per pitch compared to last season, which explains about 9 percent of MLB’s overall 4-minute increase in average game time.1Here, I am using PitchInfo data.Manfred’s rules aimed to shorten this time by forcing batters to keep one foot in the box between pitches, thus eliminating some hitters’ long and involved pre-pitch rituals. But the rule has numerous exceptions: if the hitter swings, steps back to avoid a pitch or even if he simply asks for a timeout, he may leave the box to refasten his gloves or kick the dirt. As hitters became more familiar with the rule, they began taking advantage of each exception, so that over the course of the 2015 season, time between pitches increased from just under 21 seconds at the beginning of the year to around 21.6 seconds by the end. That gradual slowing of the game’s pace has continued in 2016, with the average time between pitches swelling to 21.69 seconds.Whether because veterans command more respect or have a better grasp of the exceptions to the rules, older hitters have always moved a little slower at the plate than youngsters. In 2015, for instance, hitters older than 28 took 21.49 seconds between their pitches, while hitters age 28 and younger took 21.25 seconds.2I used age 28 because it was the median for MLB hitters in 2015, making it a rough dividing line between young and old. But this year, older hitters have widened that gap dramatically: They are taking 21.87 seconds between pitches on average, as opposed to only 21.47 for their younger counterparts. While both populations have seen their average pace decline, the difference between old and young has also expanded some 67 percent.3Older hitters tend to be more disciplined, and hitters’ counts tend to take more time to get into, so it’s possible that we’re seeing a decrease in pace as an effect, rather than a cause, of older hitters being better. However, even after adjusting for count and the presence of men on base, older hitters tend to take an additional 0.3 seconds per pitch, suggesting that the increased time is not just a result of superior plate discipline.As I wrote last year, some older hitters may derive special benefits from taking their time between pitches. Ortiz claims that the additional time lets him make better guesses about the next pitch, perhaps allowing him to offset a decline in raw bat speed with the benefit of experience. That benefit may not apply equally to less cerebral players, and so not all 40-year-olds are seeing the same success as Big Papi.But even if old hitters don’t derive any special time-related benefit relative to youngsters, they have still received the lion’s share of the extra seconds in MLB’s pace slowdown — and more time is correlated with better outcomes for hitters.4The correlation coefficients between time and linear weight value for both 2015 and 2016 were statistically significant with a p-value under 2.2e-16. This really shows up when the time between pitches exceeds 30 seconds: hitters produce an average of 0.05 runs5Using pitch-type linear weights. on those pitches, vs. -0.01 runs per pitch when hitters have 30 seconds or less to think. While there are thorny issues of correlation vs. causation here, it’s generally true that the longer a player has to ponder the next pitch, the better he fares. And this season, older hitters have gotten a disproportionate share of that extra time.Ortiz is far from the only veteran batter witnessing a late-career revival. Daniel Murphy has seen his performance soar far beyond expectations, and Robinson Cano is on pace to have one of his best seasons in 2016 after one of his worst in 2015. After years of steady decline by MLB’s senior citizens, the weighted age for MLB batters in 2015 was the lowest it had been since the early 1990s — but that figure has actually increased this season. In fact, MLB is seeing the largest single-year bump in WAR-weighted age since the strike-shortened 1994 season; before that, you have to go back to 1981 to see a similar swell.It’s hard to tell whether and how much of the resurgence of older hitters is due to additional time at the plate, vs. the many other factors which may be lengthening careers. On top of pace, we could also point to a combination of better training, medical advancements and a (potentially) juiced ball as prolonging hitters’ careers. But the next time you find yourself checking your watch mid-plate appearance, you’ll know who to blame for — and who may be benefitting from — MLB’s slower pace of play.