Wood, 35, won the last of his 58 caps at the 2003 World Cup

"Ireland seriously underperformed, never quite got the spark and only touched that spark a couple of times during the Six Nations," said Wood.

"The pressure on him has been terrible. People wanted more from this group of players," added the former hooker.

O'Sullivan resigned on Wednesday night after six and a half years in charge.

Wood added that O'Sullivan did deserve credit for resurrecting Ireland's fortunes.

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"He turned Ireland way around as we had won virtually nothing in the 1990s.

"Yet Ireland have won so many games in the Six Nations. In the history of the Six Nations we are in the top two."

Ireland hooker and BBC Sport columnist Rory Best said he had "a lot of respect for Eddie as a coach".

"He really brought my game on in the last two years and when I look at the player I am now, and think about where I was a couple of years ago, I owe him big time," he said.