The deadline for underclassmen to declare for the 2019 NFL Draft came and went on Monday. Now, teams will officially be looking ahead to replace those that they lost either to the pros, transfer or graduation. With that in mind, here are some names to watch for 2019 as they replace college football's biggest stars. 

Obviously, a list like this could be 50 players long, at least. There was no shortage of big-name, impact players from this past season and certainly plenty of capable backups ready to take their place. In the end, the list was whittled down to some of the biggest -- or most productive -- players who have at least somewhat of a clear successor carved out. Otherwise, there will be tons of competitions over the offseason, so replacing a guy like Kentucky linebacker/edge rusher Josh Allen could involve a few names. (Moreover, matching Allen's production probably takes a committee approach.) 

Additionally, some key names to watch for 2019 were mixed in. These are players who are primed to have breakout seasons and will be household names by this time next year. Let's get to it ... 

Out: Ohio State QB Dwayne HaskinsIn: Justin Fields (from Georgia) -- Fields hasn't actually received his legislative relief waiver yet to play immediately next season, and he may not receive it. However, with Haskins gone to the NFL and Tate Martell exploring his options, the writing seems to be on the walls for Fields starting next season. 

Out: Clemson DE Austin Bryant | In: Xavier Thomas -- Thomas has an argument to be the best "backup" from this past season. He still posted 10.5 tackles for loss, 3.5 sacks and four quarterback hurries -- all solid numbers for a starter, let alone a rotational player. He'll be an even bigger factor coming off the edge in 2019 when he's a full-time starter. 

Out: Oklahoma QB Kyler Murray |  In: Spencer Rattler -- Murray declared for the NFL draft on Monday, and Austin Kendall has put his name in the transfer portal. Kendall could still come back, but Rattler, the No. 1 pro-style quarterback recruit for 2019, has as good a chance as anyone on the roster. He'll have to learn quickly, though, as he doesn't arrive until this summer. Of course, a transfer in from Jalen Hurts could change everything.

Out: Memphis RB Darrell Henderson | In: Patrick Taylor Jr. -- Henderson was college football's most effective runner in 2018, but Taylor racked up 1,100 yards of his own. He'll probably be the No. 1 option in terms of carries, but the Tigers aren't afraid to mix in Tony Pollard, either. This duo is going to be a lot of fun to watch after combining for more than 2,300 yards of offense a season ago. 

Out: Michigan DE Rashan GaryIn: Kwity Paye -- Paye should slide right into the starting spot left by Gary, a surefire first-round pick, after finishing fifth last season with 5.5 tackles for loss in 13 games. He was a rotational player all of last season and stepped up in Gary's place after he missed multiple games with a shoulder injury. 

Out: LSU LB Devin White | In: Patrick Queen -- LSU will have some options to work with this spring in its quest to replace a talent like White, but Queen is in the driver's seat to get a bulk of the first-team reps moving forward. Queen had a productive second half of the season and came up big when LSU's defense was short-handed due to targeting calls against White and Jacob Phillips. Queen had nine tackles in the Fiesta Bowl win over UCF, which tied his season high. 

Out: Washington QB Jake BrowningIn: Jacob Eason -- You may remember Eason way back when he was starting at Georgia before being Wally Pipped by Jake Fromm, who has now forced two quarterbacks to transfer on this list (Fields). After sitting out a season, Eason will get the first crack at replacing Browning, who departs as Washington's all-time leading passer. 

Out: Penn State QB Trace McSorleyIn: Tommy Stevens -- You could also add Sean Clifford to this. Stevens, who has been a long time backup dating back to Christian Hackenberg days, will probably get the first shot at succeeding McSorley in spring practice, but Clifford will get an equal shot. It might end up actually being among the more interesting offseason competitions. For now, though, Stevens is probably the guy. 

Out: Oklahoma State RB Justice HillIn: Chuba Hubbard -- Hubbard was for all intents and purposes the "1B" option for Oklahoma State's ground game, but he's included here because if you don't know his name yet, you should and you will. He carried the ball nearly 10 times per game in 2018 and averaged almost six yards per carry to go along with seven touchdowns. He'll be a workhorse for the Cowboys in 2019 with first-team all-conference potential. 

Out: Houston DE Ed Oliver | In: Aymiel Fleming -- Oliver was such a stats monster along Houston's defensive line that his backups didn't get a ton of numbers of the course of the season. But when Oliver was hurt late in the year, Fleming, a junior, took over a bulk of the snaps. He finished the season with 21 tackles and a forced fumble. 

Out: USC LB Cameron Smith | In: Palaie Gaoteote IV -- Smith was a workhorse defender (when healthy) for what seems like 10 years now. However, Gaoteote could be primed for a breakout season in 2019 after finishing this past season with 38 tackles, 20 of which came in a two-game stretch in the middle of the season when Smith was limited or out with injury. 

Out: Alabama DL Quinnen Williams | In: Phidarian Mathis -- The Crimson Tide could go in a few directions with Williams off to the NFL after a monster season, but Mathis is likely to be slated with the ones first as the offseason progresses. He'll lead that group with experience after playing in every game this past season as a freshman, recording 18 tackles.