User blog comment:FairyRaven/Fairy Tail Chapter 427: Pitched Underground Battle, Review and Commentary/@comment-66.87.117.48-20150406093923/@comment-7418318-20150406094834

Gray very clearly stated that the ONLY thing he cares for right now is E.N.D. It wouldn't make sense for him being overjoyed at the prospect of fighting Natsu, since for Gray this fight is just a distraction from his goal.

You don't make a rape-face when thinking things like "What is he doing here?", "Will his appearance endanger my plans?", "Do I really have to fight him, I'd much rather go after E.N.D. than deal with this distraction." and similar stuff.