Baines, who is currently out of the side because of an injury, was a pundit for ITV's coverage of his team's 2-1 win over Dinamo Kiev.
'I'm not too sure,' said Baines, when asked whether it was Tim Howard's decision not to have a man on the near post at corners, or if the orders came from Martinez.
'We get the organisation before the game from the manager and the assistant manager before the game, so I'm not too sure who makes the final call.'
(From the Daily Mail)
So the team does get instructions on the organisation before each game.
Martinez could either instruct a man on the near post, or give Tim Howard the responsibility to make a decision during the game.
Baines wasn't at the briefing for this game, so he didn't know what the specific instructions were.
It seems clear enough to me.