Baseball players frequently put up numbers during the second half of a season that differ dramatically from what they were able to do in the first half. This can be attributed to a variety of factors. Sometimes it is a player who is young, or returning from injury, and improving as he adjusts to the level of competition. In other instances, we find the opposite affect -- that a player's performance will decline in the latter part of the season as opponents discover his weaknesses and adjust to his style of play. And of course, in some cases, the change in production is attributable simply to luck, or to a particularly good or bad stretch of play.
Whatever the case, oftentimes we can look at a player's second half and use it as a predictor as to how he will perform in the next season. It makes intuitive sense that a player is more likely to carry his performance from the latter half a season forward, rather than the early part of the season. With this in mind, let's take a look at some Twins players who saw their performance rise or fall in the second half of 2007, and judge whether or not we can expect those second-half trends to carry over into the 2008 season.
1. PAT NESHEK, RP
First half: 42.1 IP, 1.70 ERA, 52 K/13 BB, opp .129/.205/.243
Second half: 28 IP, 4.82 ERA, 22 K/14 BB, opp .260/.347/.440
Neshek's drop-off in the second half last season was dramatic, and I'd be lying if I said I wasn't somewhat concerned. However, for the time being, I am inclined to label it as a mirage. Before being shut down mid-way through September, Neshek had appeared in a total of 74 games last year. That is a ton for a guy whose previous high for an entire season was 65 (set the previous year). While his innings load (70 1/3) was not that bad, it wears a pitcher down to warm up and enter games that frequently, and indeed Neshek was shelved with two weeks left because his arm had worn down. More than likely, that's why we saw his numbers drop off after the All-Star break. He enters this season with a fresh arm after a winter of rest, and hopefully Ron Gardenhire will be a little less liberal about forcing Neshek to warm up and enter games several nights in a row just to get an out or two.
2. JASON KUBEL, OF
First half: 240 AB, .250/.302/.404, 7 HR, 37 RBI
Second half: 178 AB, .303/.379/.511, 6 HR, 28 RBI
Kubel seemed out of his element for much of 2006 after missing the entire 2005 campaign in the aftermath of major knee surgery. His struggles carried over into the early part of the 2007 season, where he appeared tentative at the plate and seemed to struggle with his pitch recognition. However, even during the hard times, Kubel always made hard contact, and as he began to regain the plate discipline that he showed throughout the minors, his numbers began to improve rapidly. Prior to the All-Star break last year, Kubel's K/BB ratio was 2.6; afterward, that number dropped to 1.4. The latter number is much more in line with his minor-league K/BB ratio of 1.1, and as such it should be no surprise that his second-half hitting line was extremely similar to this career hitting line in the minors of .320/.385/.499. Expect similar things in 2008.
3. MATT GUERRIER, RP
First half: 53 IP, 1.70 ERA, 37 K/13 BB, opp .183/.246/.253
Second half: 35 IP, 3.34 ERA, 31 K/8 BB, opp .272/.318/.463
Guerrier has always been a pretty solid pitcher, but I don't think there's really any question that he was playing way over his head in the first half last year. His luck evened out in the second half, when his ERA and opponents' OPS shot way up despite the fact that he improved his strikeout rate considerably and maintained a relatively modest walk rate. Considering his past performance and his age, I think it's much more realistic to expect an ERA around 3.34 than around 1.70 from Guerrier. Fortunately, that's still very solid.
4. JUSTIN MORNEAU, 1B
First half: 322 AB, .295/.364/.581, 24 HR, 74 RBI
Second half: 268 AB, .243/.318/.384, 7 HR, 37 RBI
Through the first four months or so of the 2007 season, Morneau continued to post numbers very similar to the ones he racked up during his MVP campaign in 2006. Then, in August and September, Morneau completely fell apart. After hammering 28 home runs through the end of July, Morneau managed a measly three home runs during the season's final 56 games. The drop-off in power isn't completely shocking, since we saw the same trend even during his magnificent '06 campaign (albeit to a much lesser degree), but in 2007 Morneau lacked a .342 second-half batting average to offset the power outage. His offensive numbers down the stretch last year were dreadful, and it seems completely inexplicable. As far as I'm aware, he had no major injuries, and the drop-off in production did not come along with a noticeable increase in strikeouts or decrease in walks. With all these facts in mind, I'm inclined to pass off Morneau's dud second half as a really bad two-month stretch, rather than a fundamental decline in ability. Considering the massive contract he recently signed, we'd better hope that is the case.