MacDonald reached his decision after bouncing back from a demoralising 6-0 defeat at Newcastle with Sunday’s 1-0 victory over Everton.
“I know that managers, from week to week, if they win a game they are great. But if they lose a game everybody dissects it. I know how tough the football industry is,” said MacDonald.
“Every time you appoint a new manager it is a major decision at any football club. You only get something like three games in the Premier League and then you are a terrible manager.
“I’d like to think that I actually think about all things, whether it is football or anything. I was not naive in thinking this was going to be an easy decision to make. I am aware of how big a decision this is.
“But the staff here have been fantastic. They have been very, very supportive and they are all keen for me to want to be involved.”
MacDonald is being hotly tipped to be appointed the successor to Martin O’Neill, who quit on the eve of the new season, imminently. United States boss Bob Bradley had been interested in the post but has signed a contract extension in his current role.