Justin Morneau, one of baseball's hottest prospects, finally got called up to the major leagues by the Twins this week. The stats crowd has been talking about Morneau since last year. They are convinced that those minor league numbers can be translated directly to major league performance. Last year when Morneau was called up, he rewarded them with a hot start including a home run in his first game. Unfortunately he faded quickly and ended up back at AAA. Some unconvinced statheads attributed this either to the Twins failing to be patient enough with him or to a lack of playing time.
This year, Morneau again started extremely hot in the International League. He was hitting well over .400 with 8 home runs going into May. The demands from the stats crowd for him to be called up became a chorus. In fact, ESPN's Rob Neyer just this week talked about how much better the Twins would be if they called him up.
Well they did. And he got zero hits while making defensive miscues that contributed to at least four extra runs by the White Sox in his first game. We will see how he does from here - one game is hardly a test. But if one looks at Morneau's performance after that hot start there is some reason for scepticism. Until he was called up, Morneau had hit about .250 for May with an even sharper drop in his slugging percentage. His hot start kept his average in the mid-300's but there is little reason to think that is any more accurate a measure of his overall ability than the mid-400's average of April. Its possible Morneua's International League numbers are just a reflection of a red-hot start, rather than a player who over-matched his competition.
And that is the problem with hot starts, their effects can linger for a long time. The same thing happened with Bobby Kielty last year. When the Twins traded him for Shannon Stewart people looked at his overall numbers and thought they were giving up a budding star. One Twins blogger even predicted Kielty would produce more than Stewart over the remainder of the year. But in truth, Kielty's numbers were based almost entirely on his hot start in April. After that, he was hitting near the Mendoza line (an average of .200). While he still drew walks, they didn't really add that much to his overall offensive value.
Kielty actually had decent stats the previous year as well. But even then, his full-season results were heavily weighted with a hot start. If one looked at his month-to-month performance, Kielty's production since he was traded last year have been far more in line with what should have been expected than his season averages when he was traded.
The Twins are seeing the same effect with Lew Ford - who started hot and has cooled off. His overall stats are still pretty good, but they are really a reflection of that hot start. At the end of the year that hot start will still be making him look better than he really is. If he continues to hit the rest of the year the way he has recently he will be a decent fourth outfielder. But no one will consider him replacing Torii Hunter as some over-enthusiastic Twins fans did during his hot start.
The flip side of the hot start is players who start out stone cold - like Derek Jeter has this year. His overall numbers may end up the same as last year but he probably won't fully make up for that cold start until September. That cold start will cast a pall over this season's averages for a long time, just as Kielty's hot start inflated his worth last year. Bobby Crosby, the heralded Oakland shortstop prospect, would be an example of a young player who started out cold hitting only .200 in April. His average now is only up to .265 and it may take him a long time to catch up with Lew Ford and he may never do that this year. That doesn't mean he is not already as good an offensive player as Ford.
In-season comparisions of players stats are interesting - but they are rarely very useful in really comparing players' current value. Sometimes that is true even over a couple of seasons. Those hot (and cold) starts can fool you.