That's better than last year, when the Pirates finished the month at 12-10, third in their division, fifth in the league, eleventh in the majors. It's worth noting that after April 30 last year, the Pirates were 86-54, the best record in the majors.
Now, April's not the most important month. In fact, per this article of mine in Baseball Prospectus, it's the least predictive month of the season. By the same token, the trends that've emerged in April need to at least be monitored.
How did they get to 15-9? Well, there are a couple overall comments. First, they team's been a little lucky, but just a little. Based on its April run differential of 128 runs scored and 109 allowed, we'd expect a record a game or so worse. Second, they haven't played a particularly tough schedule so far. Through the end of April, they'd played only four games against teams playing better than .500, going 1-3 against Detroit, while running up an 14-6 record against Arizona, Cincinnati, Colorado, Milwaukee, San Diego, and St. Louis (the Cardinals were exactly a .500 team in April). That'll change tonight when they fact the Cubs, who did not play a single .500-plus team in April, facing Arizona, Atlanta, Cincinnati, Colorado, the LA Angels, and Milwaukee.
Yet it doesn't feel like the team's been one of the best in the league, does it? Let's compare how they Pirates arrived at this year's 15-9 vs. last year's 12-10. I'm going to show you three tables, indicating how the Pirates did this year vs. last year in April. For each statistic, I'll show the raw number as well as where the team ranked in the 15-team National League. For ranks with an asterisk, it means that the lower the statistic, the better (e.g., ERA).
The offense has been a lot better than last year. The Pirates are fourth in the league in scoring and lead in both batting average and on base percentage. Note that they've cut way down on strikeouts and are getting way more walks, in each case moving from one of the worst teams in the league to one of the best. Like last year, opposing pitchers aren't throwing them a lot of pitches in the strike zone (Zone %) but the batters are much less likely to swing at pitches outside the strike zone (Chase %). Also, while the team's power ranking (isolated slugging, which is equal to slugging percentage minus batting average) hasn't moved up much, the raw number has. As Travis Sawchik pointed out over the weekend, the team's benefited from seeing more pitches. They won't stay this hot, but the offense looks strong.
One exception: Andrew McCutchen was the worst batter in the Pirates' starting eight during April, posting a .226/.339/441 slash line. But considering that he hit .194/.302/.333 in April last year, one of the worst performances in the league, then went on to be one of the top hitters in the game for the remainder of the season, it seems premature to worry.
In my preview for the team's 2016 season, I identified starting pitching as a key area of concern. Has that been borne out?
The starters have undoubtedly been worse. Their ERA is higher, and their FIP (fielding-independent pitching, a measure that's scaled like ERA but takes into account only strikeouts, walks, and home runs) has gone from best in the league to among the worse. They're striking out fewer hitters, walking more, and not lasting as deep into the game. Most worrisome to me is the chase percentage. When pitchers get opposing batters to swing at pitches outside the strike zone, it means that they're fooling hitters and, more often than not, inducing weak contact. The Pirates starters got a lot of batters to chase last year. They're not this year. If hitters lay off pitches outside the zone, they can tee off on the resulting pitches in the zone. This is a concerning trend that I'll monitor. I'm still worried about the rotation.
How about the bullpen, long a Pirates strength, but off to a slow start this year?
Well, the bullpen isn't the dumpster fire it was when I wrote the post referenced above, but it hasn't been good, and it started May with its fourth loss of the year. This is my biggest worry for the Pirates. The offense won't stay this good, but it's a good unit. The starters aren't a great bunch, but they're OK, and there are probably reinforcements on the way. But a bad bullpen? This is new, and it's disconcerting. Last season, the Pirates had nine relievers who threw at least 25 innings, and of them, all but one had an ERA below 3.00. (And the one who was above, Arquimedes Caminero, was at a not-bad 3.62). This year, of the eight Pittsburgh relievers with at least five innings pitched so far, only one's below 3.00 (and that one, Mark Melancon, isn't below by much, 2.61). They're still getting batters to chase pitches outside the zone, but they've backslid in all the components of FIP--they're allowing more home runs and walks and getting fewer strikeouts. Absent pretty marked improvement, the team is going to be challenged to hold onto late leads and overcome late deficits.
Is this whining about a good team? Perhaps. But remember, that 15-9 record came against teams that, by and large, have struggled this year. In May, the team has six games against the Cubs and three each against the Cardinals and Rangers. That's a tougher slate than the team faced in April. Some things, especially the bullpen, need to get better in order to maintain this hot start.