Everton were beaten 2-0 by Arsenal on Saturday in another disappointing performance at Goodison Park.
The Catalan manager has come in for increased criticism in recent weeks, with his side currently languishing in the wrong half of the table.
They were beaten comfortably on Saturday by Arsenal to leave them 12th in the table with just nine games of the season remaining.
Many believe that is a sign of the side vastly underachieving given the quality they have available in their squad and Keown says Martinez must improve his understanding of the game.
“It seems as if Martinez is a brilliant tactician before the game but not during. So that’s a problem for him,” he told Fletch and Sav.
“His substitutions seem to give him a problem. He’s the modern day tinker man and it doesn’t help the situation all the time.”
“He’s got to have a better understanding tactically of the game. He starts really well but he’s often dictated too much by the opposition for my liking.”
This has certainly been another disappointing season for Everton and Martinez, who could not blame their Europa League excursions as they did last season.
Most of the blame has been put at the Spaniard’s door for their issues, with some at Goodison Park questioning whether it is time for a change of manager.
That could be something that happens in future, with new investor Farhad Moshiri in particular unlikely to accept the poor performances he has seen of late for too long.