J.D. Martinez has changed his swing and approach

Last week J.D. Martinez was named player of the week and had the baseball world buzzing about his hot streak. So he should cool off now that all eyes are on him. Instead, he remained hot, going four-for-nine with two doubles, two home runs, and four RBI in the first two games of the Texas series. Going into action on Thursday, he sat atop the American League leaderboard with a .427 wOBA and a .648 slugging percentage, if you allow his 132 plate appearances to join the competition.

Rob Rogacki noted concerns with Martinez's small-sample-size success. His plate discipline is lacking, his swinging-strike rate is high, and he swings at a lot of pitches out of the strike zone.

Martinez has changed his mechanics, improving his swing path and taking a more direct path to the ball with his hands. The changes paid off with six home runs in only 24 games over the winter in Venezuela. He entered spring training with a swing designed to stay in the strike zone much longer, and expected continued success. But after 18 spring at bats, the Astros released him.

Martinez has not just changed his mechanics, but also his approach. He is swinging at more pitches, whether in the strike zone or not. This may be more an effect of success than cause, as it may be that he feels like he can hit anything lately.

While swinging at more pitches, Martinez is drawing walks in more than 6 percent of plate appearances. That is below average, but above the rate of Nick Castellanos, Ian Kinsler, Rajai Davis, and Torii Hunter.

Pitchers are throwing Martinez fewer fastballs and more sliders than in the past. This is not a situation where a player is feasting on fastballs and the pitchers have yet to adjust. His strikeout rate is above 25 percent, and BABIP is .370. Translation: he is getting lucky, balls are falling in.

When he hits a fly ball, more than 25 percent of the time it is a home run. Only three players have a higher rate, and this implies an additional measure of luck. Joe Mauer once exceeded 20 percent, leading to 28 home runs. This year he is below 5 percent, and has two home runs.

One big difference between the Astros of the last two years and the Tigers is the game situation. Batting behind Miguel Cabrera and Victor Martinez, J.D. is frequently batting with runners on base in meaningful situations. Pitchers need to throw strikes or they will dig a deeper hole. This is likely to continue. Martinez may not be able to increase the low walk rate, but he may be able to continue swinging aggressively and have good pitches to attack.

Martinez has a .260 career batting average with a below-average .307 on-base percentage and 15 to 20 home runs per full season of plate appearances. His success this year is not due to a platoon role. He has faced much more right-handed pitching this season, roughly what you would expect for a starting player, and has struggled against lefties hitting only .118 /.211 /.324. I think a .270 batting average, .315 on-base percentage, and 25 home runs per season is reasonable to hope for in his prime. But we can still hope he'll deliver more.