The hosts bowlers in fact were happy to stem the run flow as they were not getting assistance from the wicket.
Mathews, however, took the charge to go after the bowlers in his attempt to pace the scoreboard.
Chandimal, who appeared to be shaky initially, found his rhythm, hitting a six off left-arm spinner Taijul Islam.
But as it looked, Sri Lanka will head to lunch without losing any wicket, Chandimal made the first mistake of the day, trying to reverse sweep Nayeem.
Chandimal made 66 off 148 with two fours and three sixes.
He reviewed the leg-before decision in vain as the 136-run partnership between him and Mathews came to an.
Four balls later, Nayeem dismissed Niroshan Dickwell (3) with a quicker delivery that went straight to crash his stump. Nayeem added two wickets with his first day's two wickets to end 4-87.