49er TEs have been weak at recognizing defenses and finding open areas in a zone. Also adjusting routes to be the "hot read" so Kaepernick can go to them quickly when under a blitz. I don't see anything in Mangini's background that suggests he can teach this. He may be able to do it but we won't know until the season starts.
This offense needs some new thinking if it is to become more than just Stanford Part 2. I don't see how Mangini would play in that. Let's hope he has more than we have seen so far.