Drill is currently using Guava version 14.0.1, which was released March 2013. https://github.com/apache/drill/blob/master/pom.xml
Many other java projects use newer versions, however this conflicts with the Drill JDBC driver since a couple of APIs it uses are incompatible with the newer guava versions. In particular:
(The public StopWatch class constructor has been removed in favor of factory methods)
Although this seems minor, it prevents easily using Drill from a java application, since again many other open source libs will be using the latest Guava version (18).