As shown in PFR’s tracker for NFL rookie contracts, 201 of this year’s 256 draft picks have signed. That leaves 55 drafted players without formalized contracts as of this writing. 
Thanks to the collective bargaining agreement of 2011, rookie contract negotiations are not as arduous as they were in years past. Rookies, generally, will agree to terms in accordance with their slots, though there is some wiggle room when it comes to issues such as offset language. If a player is cut within his first four years and does not have offset language in his deal, he can effectively double dip by collecting on the remaining guaranteed portion of his rookie contract while earning pay from another club. With offset language, the player’s earnings will be capped as the former team can deduct the amount of his new contract from their payout.
Unsurprisingly, 13 of this year’s unsigned players are from the third round of the draft. Third round picks, historically, have been tricky for teams, even under the simplified rules of the latest CBA. Third rounders have a slotted signing bonus – like every other pick – but their base salaries can be negotiated. If a player at a premium position is selected between, say, a guard and a center, he may push for a higher base than each player, rather than using their contracts as a guide.
The bulk of the stragglers come from the first round, where 20 of this year’s 32 selections are unsigned. Players chosen within the top 32 selections, and especially those selected in the top 10, can often exert more leverage in negotiations in order to get more favorable terms from clubs. In 2016, Joey Bosa‘s talks dragged for months over the timing of his signing bonus payment. Ultimately, Bosa’s reps did not get everything they wanted, but they were able to get the Bolts to meet them in the middle.
Right now, Colts guard Quenton Nelson (No. 6 overall) and Cardinals QB Josh Rosen (No. 10 overall) are the only two players in the top ten that have signed their rookie contracts. That number will increase in the coming days, though it wouldn’t be a surprise if some of this year’s top selections do not sign until late June or July.