Jason Kipnis isn't off to a bad start this season, his batting line of .270/.315/.410 gives him a wRC+ of 102, meaning he's been a touch better than average at the plate, and when you factor in good base running and solid defense, his overall contributions so far are well above average. That batting line is a far cry from the .303/.372/.451 line he put up a year ago though, when he was one of the very best second basemen in baseball. Certainly Indians fans are hoping he can get close to his 2015 production, or at least split the difference between then and now.
Kipnis is on pace for 20 home runs, and his isolated power (ISO) is .140, very close to the .149 he posted in 2015. His power isn't missing. His BABIP of .353 is also almost an exact match for the .356 he put up last season, so it's not that either. Instead, the culprits behind the drop in his numbers from last year to this one are a huge spike in his strikeout rate and the return of his massive struggles against left-handed pitching.
Kipnis' strikeout rate right now is 28.8%, which is 16th-highest among the 194 MLB hitters with enough plate to be considered qualified. Kipnis' strikeout rate for 2014-2015 was 17.3, so his present level is a massive leap in the wrong direction. Notably, strikeout rate is one of the first statistics to stabilize (Russell Carleton's research found that strikeout rate is fairly stable after just 60 plate appearances; Kipnis already has 111), meaning that while a player on pace five weeks into the season to hit 60 home runs is not likely to actually hit or even approach 60 home runs, a player on pace five weeks into the season to strike out 200 times is probably going to finish the year with a ton of strikeouts.
Why is he striking out more? A variety of factors. According to plate discipline numbers at FanGraphs, he's swinging at slightly more pitches outside the zone (27.2%, compared to 26.7% last year), he's swinging at fewer pitches inside the zone (54.9%, compared to 62.54% last year), and he's swinging and missing a lot more (9.8%, compared to 6.9% last year).
Based on Kipnis' BABIP and hit distribution, his elevated strikeout rate has already cost him four hits, which represents a 40-point swing in his batting average. It is very, very difficult to have a strong offensive season while striking out so much, and the only way to do it is to have 30+ home run power, which Kipnis doesn't. If this strikeout rate is here to stay, Kipnis is likely limited to roughly league-average offensive production.
Notably, against right-handed hitters, Kipnis has continued to do very well; he's batting .317/.368/.500, which is excellent. Against lefties, though, the bottom has fallen out for Kipnis. Or, more accurately, the bottom has fallen out again.
Kipnis is currently batting .200/.233/.275 against southpaws, with 17 strikeouts in 43 plate appearances, which works out to 39.5%. He has just two walks and one extra-base hit. His wRC+ against lefties right now is 36. That batting line looks a lot like the one he put up against left-handed pitchers in 2014, which was .208/.256/.244, which is what I meant when I mentioned a problem returning. Last season, he wasn't good against lefties, but he hit .250/.302/.377 against them, which is both substantially better than his current line, and also pretty much league average for right-handed hitters against left-handed pitchers. His strikeout rate against lefties was 21.3%, little more than half what it is right now.
There's a lot of season left, but Kipnis' strikeout rate is concerning, and his numbers against lefties are discouraging. Kipnis isn't going to be moved into a platoon, but if he can't make some adjustments against lefties, there's going to be a huge hole near the top of the order in a lot of games this year. It was only last year that he was doing things well, and hopefully something clicks and he returns to that form soon.