there is a stat, BA Late and Close, so hits after the 6th with the game within 3 runs.  No Rockie is in the top 20 in the NL despite having 3 in the top 12 in NL BA.  With this said, clutch metrics tend to be looked at skeptically in that they are often derived from data pools that do not have a large enough statistical sampling or there is independent bias (maybe your team has a disproportionate amount of blowout wins or losses thus giving you fewer opportunities)... but none the less it does fit your narrative which I tend to agree with

http://stats.washingtonpost.com/mlb/getleaders.asp?rank=226