Shifts no doubt help, but defense is about execution and game awareness, too. I'm a huge fans of lining up the defense where guys hit the ball and pitching to the defense.
You look at Pittsburgh, and they have increased shifting over the past few years, and gotten pitchers to pitch to the defense (pullable low sinkers so that they generate grounders into the shift), and they have greatly improved their defense (2013 groundball percentage (GB%)- 52.5%, batting average on balls in play (BABIP) - .285; 2012 - 46.6%, .286; 2011 - 45.6%, .300; 2010 - 44.0%, .311). That type of pitching also improved their HRs allowed per 9 innings, and led to drops both in traditional measures like ERA but also in advanced "FIP" (a measure of Pitchers performance that is "Fielding Independent", thus FIP).
The issue with the Nationals will be, no matter how much they shift, they still need to execute. Zimmerman needs to be able to throw accurately and needs to move back so that his range improves. Desi, for all his physical gifts of range and arm, needs to continue to not force throws when he should eat the ball and has to minimize the stone hands he sometimes displays. Rendon looks like he can play second, but he still is short on reps at the position. That should continue to improve. Our two best defensive infielders for their positions, Espinosa and LaRoche, will be fine with the glove, but will have their playing time limited by their offense.
As for the pitching, Roark, Fister and Zimmermann are all groundball pitchers by nature, and Strasburg has become a very high % groundball pitcher. Among pitchers with 162+ innings, Fister was 4th in GB%, Strasburg 8th, and JZ 23d out of 81 pitchers. fister and Strasburg were over 50% groundballs, and only 13 pitchers did that. We have the starting staff to pitch to an aggressive shifting defense, so it will come down to execution by the fielders, scouting for opportune times to shift, and confidence in the strategy.
