Prosinski has appeared in 56 games with nine starts over four seasons with Jacksonville (2011-14) and Philadelphia (2014), collecting 73 tackles. He also has 27 special-teams tackles.
Reynolds appeared in 30 games with three starts for Jacksonville from 2013 to 2015.
Vereen had 38 defensive tackles and nine special-teams stops in two seasons for Chicago.
The Bears (0-3) have been busy after getting shut out for the first time since 2002 in a 26-0 loss at Seattle, trading Jared Allen to Carolina and Jonathan Bostic to New England. Chicago hosts Oakland this week.
AP NFL website: www.pro32.ap.org