Brendan Rodgers has internal priorities on his mind at Celtic alongside juggling potential transfer activity this summer. Pre-season is now here, and several fringe players will have a chance to lay it all on the line and convince the manager they are worth a first-team slot this coming campaign. There may be added motivation for peripheral figures to seize their opportunity. Squad places are up for grabs, and with no new arrivals announced, the next few weeks could be invaluable for one or two. Celtic take on Ayr United and Queens Park before jetting off on a three-match tour of the United St…