San Francisco 49ers v Baltimore RavensWith the 2021 NFL draft now just three days away, NFL teams will have their main targets and backups in place on their respective boards.Some of those poised and primed teams can now switch their attention back to the free agency pool to buttress the positions on the roster they don't expect to fill during the 2021 NFL draft.There are several elite talents still available and, as with every season, there is a distinct possibility that more than a couple of these stars will get snapped up before the draft.But which of the players still loitering in the free agency market are most likely to be signed up between now and Thursday?Let's have a look.Top 5 free agent signings likely to happen before the 2021 NFL draftThe #Bucs will be re-signing Antonio Brown soon, according to @NFLSTROUD pic.twitter.com/nPnZOh92zL— Dov Kleiman (@NFL_DovKleiman) April 21, 2021#1 - Antonio Brown, WRLos Angeles Rams v Tampa Bay BuccaneersMost NFL free agents with six straight Pro Bowl appearances on their CV won't have too much of an issue finding a new team. But then, most NFL players aren't Antonio Brown.The NFL's enigmatic bad boy hasn't signed on for another year with the Tampa Bay Buccaneers just yet and is still available to potential suitors.Brown settled his civil suit with a former female trainer earlier this week, though, and, according to recent reports, is a target of both the Bucs and the Baltimore Ravens.Brown registered 483 receiving yards in half a season for Tampa in 2020. He also caught a crucial touchdown pass in the Super Bowl. If Brown isn't snapped up before the draft, expect to see him posing in a fresh uniform shortly after.#2 - Richard Sherman, CB10 years ago the #Seahawks drafted a CB in the 5th round. Some scouting reports suggested he was a tick slow, had stiff hips, undisciplined eyes & inconsistent route recognition. Richard Sherman ended up being one helluva pick. Here’s how it came to be. https://t.co/TMsmE3c2H4 pic.twitter.com/gmlreNsHY9— Dugar, Michael-Shawn (@MikeDugar) April 22, 2021Legendary CB Richard Sherman might be in the twilight of his career, but in the right coverage scheme, he's still got plenty to offer.Despite having added significant talent to the roster during the free agency window, the New York Jets still have $28.3 million in cap space. Outside of the excellent Marcus Maye, the Jets have one of the worst coverage units in the entire NFL based on their combined performances in 2020 and were justifiably ranked 29th by PFF.With new coach Robert Saleh familiar with Sherman's skillset from their time spent working together in San Francisco, there's still a chance Sherman winds up in New York before Thursday.#3 - Alejandro Villanueva, LTFormer Steelers tackle Alejandro Villanueva is visiting the Ravens this week, per @RapSheetVillanueva: 77.8 pass-block grade in 2020 (T-23rd) pic.twitter.com/INHmJ4GLNL— PFF (@PFF) April 19, 2021Like many, I was shocked to see the Pittsburgh Steelers release their starting left tackle, Alejandro Villanueva, last month. The veteran started practically every game and has been an important cog in the Steelers O-line for the entirety of his six-year career thus far.A piece of interesting free agent news: #Steelers FA OT Alejandro Villanueva is set to visit the #Ravens this week, league source said. With some moving parts on Baltimore’s O-line, they plan to check out Villanueva in person.— Ian Rapoport (@RapSheet) April 19, 2021Recent reports from Ian Rapoport and NFL.com indicate that Villanueva is set to meet with the Ravens to discuss a potential deal for the 2021 season.Villanueva would be an experienced and capable replacement for Orlando Brown Jr., who was traded to the Kansas City Chiefs last week. There is every chance that this deal gets done either before or shortly after the NFL draft.Alternatively, if the Steelers don't manage to draft a capable replacement for Villanueva this week, he could end up back in the Steel City.#4- Casey Hayward Jr., CBCasey Hayward Jr. = 🔒 pic.twitter.com/jbBKXpGGn8— PFF (@PFF) June 8, 2020One of the game's elite CBs over the past decade, Casey Heyward Jr. may have endured one of his most inconsistent seasons in the Chargers secondary in 2020. Still, he held opposing receivers to under 25 receiving yards in around half the games he featured in.As mentioned, the Jets need to buttress the coverage unit before the 2021 NFL season gets underway. Hayward signing for the New York Jets is more of a hunch than anything else. But his ability to play on the boundary would be perfect for the team.If Saleh's defense walks out on September 9th with Maye and Hayward Jr. in the defensive backfield, the Jets will have a great chance of improving on that lowly-ranked PFF grade mentioned earlier.The Seattle Seahawks are another viable destination for the former Los Angeles Charger.#5 - Sheldon Richardson, DTCleveland coach Kevin Stefanski on Sheldon Richardson: 'I hope that there's a scenario' he returns to the Browns https://t.co/7oUsYGCjPb— The Browns Wire (@TheBrownsWire) April 20, 2021Browns coach Kevin Stefanski is on record stating that he would like to bring DT Sheldon Richardson back to Cleveland for another season.It's hardly a surprise, as Richardson was the Browns' second-highest rated player in their long-awaited playoff victory over division rivals the Pittsburgh Steelers last season. He was a top performer throughout the campaign as well.The Browns still have just over $10.7 million of available cap room and if Stefanski doesn't wish to pluck a new DT in the NFL draft, there's every chance that Richardson will make a return to Cleveland.