While the leader has the lancer the tough guy has the smart guy. The smart guy is what the name says the smart person in the group, they are excellent in technology, and they are masterminds of manipulation and politics. In a fantasy setting the smart guy is a wizard who loves to research.
The smart guy is important to the team because without the subtle control of people, or certain knowledge the team can be at a big disadvantage. The smart guy can never be seen in person like Wade from Kim Possible, or they can still be in the thick of battle just not in the same case as the tough guy. While the smart guy may be the “weakest” in the group that does not mean that they can handle themselves but that compared to the rest of the team they are more auxiliary in function, and may not be the best fighter in the group.