I guess I just don't have any recollection of Papi ever expressing that he felt that way...he may have griped about his own contracts, sure, but never about adding talent from outside the system. The guy was lobbying for another big bat basically from the day Manny was traded.
If we add a Stanton or Martinez this offseason, I can't see any of our young players' reactions being "Oh s***, there goes that extension I wanted...curse you, Desperate Dave!" By and large, players seem to appreciate a front office that is proactively trying to improve rather than sitting on what they already have. As Moon said, these guys know how the system is set up...and I'm willing to bet that in the cases that are now just 2-3 years from free agency (Bogaerts/Betts/Bradley), the sides have already felt out what interest there might be in an extension and what it might take to get it done, and any external acquisitions likely aren't going to be the determining factor in whether that happens or not.