Nick Foles is killing it right now ... but when Carson Wentz gets healthy, the starting QB job in Philly is HIS ... so says Eagles legend Brian Westbrook.
Westbrook -- who's in the Eagles Hall of Fame -- tells TMZ Sports he's incredibly proud of the job Foles has done filling in for Wentz, but even if he wins the Super Bowl ... he won't get the starting nod next season.
"When Carson Wentz is healthy, Carson Wentz will be the starting QB of the Eagles."
The good news for Foles ... Westbrook says the guy has a real chance to score a massive contract somewhere else, but the future in Philly is definitely Wentz.