Brown left training camp Wednesday with tightness in his right hamstring. Slaughter was waved/injured Wednesday after spraining his left foot Tuesday.
Brown and Slaughter bring the total to seven receivers on the sideline for the Jaguars. Jacksonville already was without Cecil Shorts III (hamstring), Allen Robinson (hamstring), Tandon Doss (ankle) and Ace Sanders (leave of absence). And Damian Copeland (wrist) was placed on injured reserve last week.
The 6-foot-6 Barden, a third-round draft pick by the New York Giants in 2009, caught 29 passes for 394 yards in four seasons.
The 5-foot-8 Hall totaled 16 receptions for 155 yards and two touchdowns in three seasons with Philadelphia and Kansas City.
Jaguars RB Toby Gerhart to miss preseason opener
Jacksonville Jaguars running back Toby Gerhart will miss the team's preseason opener against Tampa Bay.
Coach Gus Bradley ruled Gerhart out Wednesday, two days before the game.
Gerhart has missed the last five days of practice because of a hip flexor injury. Without him, journeyman Jordan Todman has been getting repetitions with the first-team offense.
The Jaguars gave Gerhart a three-year contract worth $10.5 million in March to replace Maurice Jones-Drew. Gerhart spent the last four years backing up All-Pro running back Adrian Peterson in Minnesota, totaling 1,305 yards rushing and five touchdowns.
Jacksonville signed him to be its starter, expecting him to get around 15 to 20 carriers a game.
Now, though, the Jags are just trying to get him healthy enough to practice and play.