[DC 86]

Not sure that I agree that downside of returning is greater than the upside.  The NFL pay scale for rookies is almost logarithmic with major jumps in contract value as you approach first round and second round.  How many of the seniors drafted in the first two rounds would have been drafted as highly the prior year had they come out early? A lot of them made a lot of money their senior year in improving their draft position.

Looking at the 2017 draft which was dominated by underclassmen, there were 12 seniors drafted in the first round, of whom three still had eligibility.

Corey Davis (WR): 78-1408 with 15 TD as a sophomore, 90-1436 with 12 TD as a junior, decided to return for his senior season and recorded 97-1500 with 19 TD. Perhaps improved his stock marginally but at the risk of injury and performance decline, as well as a year of wear and tear which could reduce the length of his NFL career.

Mike Williams (WR): broke a bone in his neck as a junior and missed almost the entire season so he was compelled to return for his senior year. Was still an early entrant since he had been issued a medical redshirt.

Hasson Reddick (DE): a walk on who didn't receive a scholarship until his senior year and then had a monster year and declared for the draft. Actually was an early entrant since he had redshirted.

Jonathan Allen (DL): as a junior he recorded 12 sacks, 14.5 TFL and 2 forced fumbles, decided to come back for his senior year, recorded 10.5 sacks, 16 TFL and 0 forced fumbles. Two weeks before the combine had surgery on both shoulders which resulted in dropping to 17th overall, thus probably would have been drafted higher in 2016.

O.J. Howard (TE): 38-602-2 TD as a junior, 45-595-3 TD as a senior. Probably didn't change draft stock significantly.

Jarrad Davis (LB): 94 tackles, 11 TFL, 3.5 sacks, 1 interception, 1 forced fumble as a junior. 60 tackles, 6 TFL, 0 interceptions, 0 forced fumbles as a senior when he missed four games due to injury. Hurt his draft stock by returning.

Evan Engram (TE): 38-662-2 as a sophomore, 38-464-2 as a junior, 65-926-8 as a senior. Helped his draft stock by returning for his senior year after a disappointing junior year in which his ypc dropped from 17.2 to 12.2.

Takkarist McKinley (DE): only had six career sacks heading into his senior season so declaring for the draft wasn't a realistic option as a junior, then had a big senior season (10 sacks and 18 TFL).

TreDavious White (CB): All-SEC second team as a junior and projected as a late first round pick, All-SEC first team as a senior and drafted #27 overall. Possibly improved his draft position marginally or not at all.

Taco Charlton (DE): 5.5 sacks and 8.5 TFL as a junior, 10 sacks and 13.5 TFL as a senior, definitely improved his draft stock.

Reuben Foster (ILB): 73 tackles (48 solo) and 8 TFL as a junior, 115 tackles (60 solo) and 13 TFL as a senior. However, as a senior he suffered a torn rotator cuff and off field difficulties which dropped him to #31 overall. As a result it's not clear if returning helped him draft-wise or not despite his superlative season.

Ryan Ramczyk (T): played two years in division III and then had to sit his junior year when he transferred to Wisconsin, so coming out as a junior was not an option. Still have a year of remaining eligibility when he declared for the draft.

Summary:

Williams, Reddick, McKinley and Ramczyk weren't draftable after their junior years due to either injury or limited performance.

C. Davis, Howard and White didn't appear to materially change their grades as seniors.

Allen (definitely) and Foster (possibly) were drafted lower than they would have been as juniors due to injuries incurred as seniors.

J. Davis could have been drafted as a junior, definitely lowered his stock by returning to school.

Engram and Charlton could have been drafted as juniors, definitely raised their stock by returning to school.

There are certainly exceptions such as Engram and Charlton, but when considering the finite number of snaps in the human body, time value of money and injury risk I still maintain that in general it's financially prudent to declare for the draft as a junior. Of course it depends on the individual, but there just aren't many players who play themselves into the top of the draft by returning for their senior seasons.

[DC 86]

Not sure that I agree that downside of returning is greater than the upside.  The NFL pay scale for rookies is almost logarithmic with major jumps in contract value as you approach first round and second round.  How many of the seniors drafted in the first two rounds would have been drafted as highly the prior year had they come out early? A lot of them made a lot of money their senior year in improving their draft position.

Looking at the 2017 draft which was dominated by underclassmen, there were 12 seniors drafted in the first round, of whom three still had eligibility.

Corey Davis (WR): 78-1408 with 15 TD as a sophomore, 90-1436 with 12 TD as a junior, decided to return for his senior season and recorded 97-1500 with 19 TD. Perhaps improved his stock marginally but at the risk of injury and performance decline, as well as a year of wear and tear which could reduce the length of his NFL career.

Mike Williams (WR): broke a bone in his neck as a junior and missed almost the entire season so he was compelled to return for his senior year. Was still an early entrant since he had been issued a medical redshirt.

Hasson Reddick (DE): a walk on who didn't receive a scholarship until his senior year and then had a monster year and declared for the draft. Actually was an early entrant since he had redshirted.

Jonathan Allen (DL): as a junior he recorded 12 sacks, 14.5 TFL and 2 forced fumbles, decided to come back for his senior year, recorded 10.5 sacks, 16 TFL and 0 forced fumbles. Two weeks before the combine had surgery on both shoulders which resulted in dropping to 17th overall, thus probably would have been drafted higher in 2016.

O.J. Howard (TE): 38-602-2 TD as a junior, 45-595-3 TD as a senior. Probably didn't change draft stock significantly.

Jarrad Davis (LB): 94 tackles, 11 TFL, 3.5 sacks, 1 interception, 1 forced fumble as a junior. 60 tackles, 6 TFL, 0 interceptions, 0 forced fumbles as a senior when he missed four games due to injury. Hurt his draft stock by returning.

Evan Engram (TE): 38-662-2 as a sophomore, 38-464-2 as a junior, 65-926-8 as a senior. Helped his draft stock by returning for his senior year after a disappointing junior year in which his ypc dropped from 17.2 to 12.2.

Takkarist McKinley (DE): only had six career sacks heading into his senior season so declaring for the draft wasn't a realistic option as a junior, then had a big senior season (10 sacks and 18 TFL).

TreDavious White (CB): All-SEC second team as a junior and projected as a late first round pick, All-SEC first team as a senior and drafted #27 overall. Possibly improved his draft position marginally or not at all.

Taco Charlton (DE): 5.5 sacks and 8.5 TFL as a junior, 10 sacks and 13.5 TFL as a senior, definitely improved his draft stock.

Reuben Foster (ILB): 73 tackles (48 solo) and 8 TFL as a junior, 115 tackles (60 solo) and 13 TFL as a senior. However, as a senior he suffered a torn rotator cuff and off field difficulties which dropped him to #31 overall. As a result it's not clear if returning helped him draft-wise or not despite his superlative season.

Ryan Ramczyk (T): played two years in division III and then had to sit his junior year when he transferred to Wisconsin, so coming out as a junior was not an option. Still have a year of remaining eligibility when he declared for the draft.

Summary:

Williams, Reddick, McKinley and Ramczyk weren't draftable after their junior years due to either injury or limited performance.

C. Davis, Howard and White didn't appear to materially change their grades as seniors.

Allen (definitely) and Foster (possibly) were drafted lower than they would have been as juniors due to injuries incurred as seniors.

J. Davis could have been drafted as a junior, definitely lowered his stock by returning to school.

Engram and Charlton could have been drafted as juniors, definitely raised their stock by returning to school.

There are certainly exceptions such as Engram and Charlton, but when considering the finite number of snaps in the human body, time value of money and injury risk I still maintain that in general it's financially prudent to declare for the draft as a junior. Of course it depends on the individual, but there just aren't many players who play themselves into the top of the draft by returning for their senior seasons.