Mourinho's former assistant does not believe the 55-year-old will be short of offers.
"He'll look at the market in the future and I'm pretty sure one of the top clubs in Europe will come calling soon and offer him another job. He's a serial winner."
Clarke said it was hard to characterise Mourinho's tenure at United as being a "failure".
"He won three trophies -- the Community Shield, the Europa League, the League Cup; so it's three trophies more than Liverpool in the same period, more than Tottenham," Clarke added.
"So was he a failure or was he not a failure? I'm not sure. He finished second last year."