The thing I guess I have considered and you haven't JV in my reasoning is team morale, which is something a coach has to take into account.
Unhappy teams don't play well. Whilst the coach has the responsibility to win he needs to think about big picture stuff and not single players... and he may think this may be the difference between winning and losing...
Perhaps Marco's German is not as good as the coach would like and he believes that this combined with him not knowing his team mates may hamper the team in the short term.
Cunningham didn't start straight away for us... what was Ernie thinking?
Arguebly one of the reasons Ricki had any success was the fact the players played for each other and had a real team ethos, hard for a newbie to add to that straight away.
Man Utd doesn't work for me as a comparison. The players they buy in are world class, something Marco is not.