On the night of Friday, August 19, Tyler Naquin provided the Cleveland Indians with what is to this point the highlight of their season, hitting a walk-off inside-the-park home run to beat Toronto. It was the first play like that for the Indians in a full century, and it was awesome. At the end of that play, Naquin was batting .316/.377/.603, with a wRC+ of 158, and was one of the two leading candidates for American League Rookie of the Year.
In the month since that incredible moment though, Naquin has hit just .238/.351/.286, with a wRC+ of just 74. He has struck out in 33.8% of his plate appearances during that time, with only three doubles and not a single home run. It's hard to say he's been unlucky, given that his BABIP during this time has been .395. His already high strikeout rate has climbed, his very high BABIP hasn't been as high, but the biggest culprit seems to be the quality of his contact. Up through August 19, his hard-hit percentage (found at FanGraphs) was 42.0%, but since that day it's been only 26.3%.
Earlier in the year, Naquin was killing the ball when it was thrown near the center of the zone, or when it was low and, but pitchers have adjusted, and he's not seeing as many pitches there. Instead he's getting more pitches up in and just above the zone, and generally having a more balanced attack thrown at him.
Here's his zone chart (from Brooks Baseball) for earlier in the season:
...and here is his chart for the last month:
Because Naquin was so good early on, his batting line for the season is still the best among any of the ten Indians players with 200+ plate appearances. During the last month though, his poor hitting and questionable routes in center field have combined to make him a replacement level player.
With two of the team's top three pitchers likely out for the season, the lineup is likely going to have to shoulder more weight if the team is going to be successful in the postseason. In recent weeks it appears pitchers have made adjustments in their approach to facing Naquin, and whether he's worn down by his first season in the Major Leagues, or just hasn't been able to adjust to those adjustments, he isn't producing at a level that can help the team win. Perhaps some additional time spent watching video and working on things in the bating cage can get him turned back around, I don't know. As is, Naquin's struggles make center field an area of weakness for the Tribe, even if looking at Naquin's overall numbers this season would seem to say otherwise.