4. TE Sam LaPorta
LaPorta became the best tight end on the Lions' roster the moment he was drafted last year. All he did as a rookie was set the NFL record for receptions by a rookie tight end, and set every single-season record for a Lions' tight end regardless of experience.
As a second-round pick, LaPorta will be on a similar timeline for a new contract as St. Brown was as a fourth-round pick (heading into the final year of his rookie contract). But that conversation is not coming just yet, as LaPorta refines his game heading into Year 2. There's a chance he becomes the highest-paid tight end in the league when it comes time for his second contract.
But for now, LaPorta is a somewhere around a top-five tight end in the league with a cap hit that's currently 42nd at the position ($2,151,361). That's the simplest definition of underpaid there can be.
3. DT Alim McNeill
McNeill has progressed year-to-year in each of his first three NFL seasons, with a breakthrough last season (five sacks, etc.) that had him as Pro Football Focus' seventh-highest graded defensive tackle (86.8 overall). As he eyes taking another step this year, the booming defensive tackle market from this offseason is music to his financial ears.
There's an angle that suggests McNeill could be the odd-man out as the Lions continue to dole out contract extensions. But Holmes likes to reward those who earn it, and McNeill has certainly done that with the work he has done to improve his game, reshape his body, etc. It's only naturally he would be rewarded in-kind, and the Lions will be the team to do it.
But this year, the last year of his rookie contract he moves toward possibly earning his first career Pro Bowl selection, McNeill looks like a fantastic bargain with a cap hit just shy of $3.4 million.