You never know which undrafted rookies will make the Green Bay Packers' final 53 any given year.
But you know at least one will, and likely more. Since Ted Thompson became general manager in 2005, the Packers have the most snaps from undrafted players in the NFL at 77,079, according to ESPN.com, with the next-closest team well behind at 54,105.
The Packers signed 17 undrafted rookies this year and got their first look at them in this weekend's rookie minicamp. Here are three to keep an eye on in training camp, when the pads go on and jobs are won:
■ Matt Rotheram, G/C, 6-foot-5, 325 pounds, Pittsburgh: Rotheram might be the Packers' best undrafted signee this year regardless of position, and they didn't draft an offensive lineman, so his chances look promising.
The Packers' top two backups on the line are Don Barclay (both guards, right tackle) and JC Tretter (center, both guards, maybe right tackle). Rotheram has a shot at surpassing Lane Taylor, who was an undrafted rookie himself in 2013, for the No. 8 spot as a backup guard and center.
Rotheram played right guard and right tackle at Pitt — he started every game his final three seasons — and the Packers worked him at guard in minicamp Friday and Saturday. Still, he practiced occasionally as the No. 3 center in college, so the position isn't foreign to him. And several teams before the draft told him they projected him at center.
"(Center) might actually end up being my best position, I'm just not sure," he said Saturday.
He has great size for any of the inside positions on the line, though in physical testing his biggest shortcoming was upper-body strength. His 22 bench-press reps were short of the 26 needed to crack the top 50 percent of all guards who worked out at the NFL combine from 1999 to 2013, according to research by Tony Villiotti of National Football Post.
The Packers targeted Rotheram as a priority undrafted free agent and brought him in this spring for one of their 30 visits with draft prospects in what in effect was a recruiting visit. Their offensive line coaches joined him to watch videotape from his college career and of the Packers to show how his skills matched their offense, and they had him work on the grease board to make sure he could handle what they do mentally.
He chose the Packers over the Steelers, Vikings and 49ers.
"I was offered more bonus money by a couple other teams," Rotheram said, "but I turned that down to come here because I thought I had the best opportunity to make the 53-man roster here."
■ ILB Tavarus Dantzler, ILB, 6-15/8, 237, Bethune-Cookman: Might be the sleeper of this undrafted class because of his interesting combination of size and speed.
Dantzler played outside linebacker in a 4-3 scheme in college but projects to inside linebacker in the Packers' 3-4. His numbers last season (81/2 tackles for loss, one sack) were good but not great for an NFL prospect at the FCS level.
Regardless, there are roster spots for the taking at inside linebacker because the Packers cut A.J. Hawk and Brad Jones, and lost Jamari Lattimore in free agency. Several young, unproven players are going for those spots, with fourth-round pick Jake Ryan having the best shot at playing time this year.
But Dantzler will get his shot at probably two open roster spots among five players. The others are two players who moved from outside linebacker to inside linebacker last year, Carl Bradford and Nate Palmer; practice-squad holdover Joe Thomas; and street free agent Josh Francis.
Dantzler didn't go to the NFL combine, but at regional combines and his Pro Day he tested similarly to Ryan: 4.66 seconds in the 40 to Ryan's 4.65; 351/2-inch vertical to Ryan's 341/2; 10-1 broad jump to Ryan's 10-0; and 21 bench reps to Ryan's 20.
The 40 time is hardly the be-all, but if nothing else it shows Dantzler's straight-line speed is a little faster than Bradford (4.74), Palmer (4.71) and Thomas (4.70). Francis ran 4.65 coming out of West Virginia two years ago.
The Packers brought Dantzler in for a visit this spring.
"I sat down with the coaching staff, they basically showed me the position I'd be playing on film," Dantzler said Saturday. "It was a good fit. I feel like I can get the maximum of my potential playing that role and that linebacker."
■ John Crockett, RB, 5-113/4, 217, North Dakota State:The Packers have an opening at No. 3 running back, and Crockett's chances have to be as good as anyone's.
He, practice-squad holdover Rajion Neal and undrafted rookie Alonzo Harris are the three players going for that job for now. The Packers had agreed to a contract with another undrafted rookie back as well, Malcolm Agnew of Southern Illinois, but he presumably failed his physical, because the Packers never signed him.
Crockett was the top rusher for a North Dakota State team that won the FCS national championship the past three years. He ended up there because he was an academic non-qualifier coming out of high school in Minneapolis. Last season, he rushed for nearly 2,000 yards (1,994) and averaged 5.4 yards a carry.
Crockett was a combine invitee and tested well enough but not great: His 4.57-second 40 barely put him in the top half of "large" (210 pounds or more) running backs, according to Villiotti's research. His 40-inch vertical jump, on the other hand, ranks in the top 10 percent of any position.
Crockett said about 20 teams tried to sign him after the draft, and he chose the Packers over Oakland, Baltimore, Atlanta, Washington and Cincinnati.
"(The Packers) called around the sixth round, they said if they were looking at a back they were going to take me," he said. "But at the end of the day, they still showed they had that interest."
— firstname.lastname@example.org and follow him on Twitter @PeteDougherty.