Concussions suffered by three quarterbacks and a running back Sunday has prompted NFLPA executive director DeMaurice Smith two renew his call for the league to hire “concussion specialists” with no team affiliation who would man the sidelines to oversee concussion protocols and treat players.The players’ union continues to be frustrated over what it perceives to be an inconsistency among teams to adhere to concussion guidelines.The concussions suffered Sunday by quarterbacks Michael Vick, Jay Cutler, Alex Smith and running back Fred Jackson drew particular attention Monday from the union, which will review the injuries and adherence to guidelines based on initial observations, NFLPA sources said. Players are entitled to file a grievance if they want to pursue claims against teams. Union sources say most players are reluctant to file complaints for fear of decreased job security.Only one of the defensive players involved on the hits to the quarterbacks is under league review for potential discipline, a source told ESPN. Texans linebacker Tim Dobbins drew a penalty flag for a helmet-to-helmet hit on Cutler and could be fined.Smith suffered a concussion when tackled by Rams linebacker Jo-Lonn Dunbar. Vick left with a concussion after being hit by Cowboys linebacker Ernie Sims. Neither of those hits were penalized and the league has determined both were perfectly legal.NFLPA sources said the union wants the league to accept responsibility for creating a disciplined, prompt and safe environment for players who are injured during the course of a game. They said the union wants concussion specialists, paid not by the teams but by the league, to assume the duties of caring for players, in accordance with normal employer workplace oversight.In last year’s collective bargaining negotiations, the union gained access to player medical information and the ability to conduct its own reviews of how teams evaluate and treat all injuries, including head and neck trauma.