On Sunday, the Diamondbacks traded a pair of players at AA Mobile, Marc Krauss and Bobby Borchering, to the Houston Astros for 3B Chris Johnson. Krauss and Borchering are two players who profile as potential power hitters, but poor fielders, so they might be better fits with the Astros, who will be shifting to the American League (with the DH) in 2013. Krauss, in particular, has had a very good season with the bat, and might compete for a Major League roster spot next year. Borchering is still struggling at the AA level, and probably needs at least two more years in the Minors. While both still have potential, the Diamondbacks were willing to risk trading them to upgrade at Third Base with Johnson.

Third Base has been a weak spot for the Diamondbacks all season, as the team's 3B have combined to hit only .227/.282/.342 (.624 OPS), which is more than 100 pts lower in OPS than every other position on the team. Johnson was batting .279/.329/.428 for the Astros, with 8 HR and 41 RBI, and is expected to be the primary 3B for the Diamondbacks over the final two months of the season, replacing the combination of recent call-up Ryan Wheeler and Willie Bloomquist. Based on his play this year, Johnson should be an offensive improvement for the team, but his defense could be a concern. The basic summary for Johnson is this - a decent batting average with a lot of line drives, low walks, high strikeouts, decent power, odd platoon splits, and he's a below-average defender despite a strong throwing arm.  Let's take a closer look at Johnson.

2009 24 HOU 11 22 1 2 0 1 1 6 .091 .130 .091 -39 -50
2010 25 HOU 94 341 40 105 11 52 15 91 .308 .337 .481 121 120
2011 26 HOU 107 378 32 95 7 42 16 97 .251 .291 .378 85 80
2012 27 HOU 92 341 36 95 8 41 23 92 .279 .329 .428 105 107
TOT 304 1082 109 297 26 136 55 286 .274 .314 .421 100 99

One stat immediately jumps out about Johnson - the poor strikeout-to-walk ratio. It's been a little better this year (4:1), but Johnson is still only walking in 6.3% of his plate appearances, while striking out in 25%. Because Johnson walks so infrequently, his OBP has never been very high despite some solid batting averages. 

A closer look at Johnson's stats shows another interesting feature - he hits a lot of line drives. This year, his line drive rate of 26.8% is 3rd best in the National League, and over the last three seasons, he has a 24.6% line drive percentage, behind only Freddie Freeman, Joey Votto, and Todd Helton.  Related to this high line drive rate, Johnson has a very high BABIP (Batting Average on Balls in Play) of .353 over the last three seasons, 6th best in the NL. 

2010 2011 2012
Line Drive Rate 24.0% (3rd in NL) 23.2% (#25 in NL) 26.8% (#3 in NL)
BABIP 0.387 (1st in NL) 0.317 0.360 (#9 in NL)

Johnson also has some interesting platoon and home/road splits in his career.

vs RHP  813 230 20 97 42 216 .283 .324 .440 .764
vs LHP  269 67 6 39 13 70 .249 .285 .361 .646

Johnson has a solid .764 OPS against RHP, but drops all the way to .646 vs. LHP. A typical platoon split for right-handed batters is about a 50 point OPS improvement against LHP, but Johnson has dropped by over 100 points. He only has 269 career ABs against LHP, so it might just be a small sample size fluke, but he has hit better against RHP in each of the last three years. If his hitting against LHP was "typical" he would be a very valuable hitter. 

A glance at Johnson's Home/Road splits in 2012 is also puzzling, as he has a .937 OPS at home, with all 8 HR, and only a .550 OPS on the road. But in both 2010 and 2011, Johnson hit much better on the road, so this year's splits should not be a significant concern.

2012 Home 181 59 8 29 .326 .390 .547 .937
2012 Road 160 36 0 12 .225 .256 .294 .550
2011 Home 186 43 2 21 .231 .284 .317 .601
2011 Road 192 52 5 21 .271 .299 .438 .737
2010 Home 154 45 6 24 .292 .313 .455 .767
2010 Road 187 60 5 28 .321 .357 .503 .859

So offensively, we know that Johnson is a batter who hits a lot of line drives, doesn't walk much, strikes out a little too often, and has had a reverse platoon split so far in his career. Defensively, the data is pretty bad. Both UZR at FanGraphs and Defensive Runs Saved at Baseball-Reference have Johnson as one of the worst defenders in the league at 3B, costing around 10 runs per year with his glove. The Fans' Scouting Report is not much better, with Johnson earning a score of 35, near the lowest in the Majors (but still higher than Josh Bell and Mark Reynolds!). The only part of his defensive game that is rated highly is his arm strength. The good news about his defense, if there is any, is that it supposedly has looked a little better this year, which might get him up to adequate from bad. He does seem to have good tools, so he should be a good test for the coach Matt Williams' teaching skills.

The Diamondbacks have basically swapped out Ryan Roberts for Chris Johnson at 3B, with Marc Krauss and Bobby Borchering also going away and infielder Tyler Bortnick coming back. Roberts was given 90 games to show something with the bat, and the team got tired of waiting for him to come around. Johnson has certainly hit better than Roberts this year, and makes only $0.5M in salary compared to Roberts' $2M. He is also younger, giving the team an inexpensive option for next year or until Matt Davidson is ready for the Majors. The hope is that Johnson's line drive hitting style adapts well to Chase Field, and that his defense is not terrible, but just close to average. The Diamondbacks are only 4.5 Games Behind in the NL West, so they still have a realistic chance to make the playoffs, and Third Base is certainly a position where there is lots of room for improvement.

Edit: The Diamondbacks made room for Johnson by designating Lyle Overbay for assignment. While Overbay has hit .292/.367/.448 for the year, he had gone 2 for 25 over the last month, with 11 strikeouts and just one walk. That means that Ryan Wheeler and Chris Johnson could see occasional playing time at 1B behind Paul Goldschmidt.