"Financially we made a profit and I think we had a player who had decided it was time to move on," he told the Sunday Sun.
"I don't think we had any alternative. There are times when you can convince a player it's right to stay, and times when you can't. He did really well in my first season as manager, and scored crucial goals for us.
"But he was ready to leave. You've then got to get the best deal you can for the club, and I think we did that. There are times as a club when we have to decide when to sell.
"We've sold quite well in terms of the fees we've got for players over the last couple of years. When I took over there'd been a long time since we'd sold a player for profit and we ended up letting players go for nothing or paying players off.
"So it was a better scenario for us as a club to actually get good money for a player, and I'm pleased with the squad that we've got.
"Someone like Yakubu's always going to score goals, he's a goalscorer and there'll always be a place in your side for a player like that.
"I enjoyed working with him, he's a nice kid, quite quiet but always someone who wanted to learn and play and score goals. He'll do that for Everton just as he did for us."