The centre back looked as if he was going to be leaving Griffin Park at the end of last season with no new contract on the table.
However, after James Tarkowski forced through a move to Burnley by going on strike, the club decided that Dean was indeed worth a new deal.
Smith said: “He's matured a lot. Just the experience of being in the Championship, taking on responsibility and he's becoming a leader.
“He's a likeable lad. He wears his heart on his sleeve but he's very respectful to others.”
Dean is the type of person who wears his heart on his sleeve and is passionate about the work he does.
However, he does not let his passion get the better of him and he is known to be supportive of young players in the side, such as Josh Clarke.
Smith added: “He's streetwise. He understands he has to be respectful as well. He's very tactful amongst the players but also very helpful with the younger players.
“He's matured as a person and becoming a father will help that as well.”
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