Paul Pierce didn't rule out an improbable reversal of fortune for the Celtics after yesterday's practice at The Sports Authority Center in Waltham.

Pierce said the Celtics are determined to avoid a series sweep when they host the New Jersey Nets in Game 4 of the NBA Eastern Conference semifinals tonight (TNT, 8 p.m.) at the FleetCenter.

``I still feel confident about our team. I think the series is still long from over,'' said Pierce, who sounded both subdued and confident in his analysis of the team's state of affairs. ``I never thought we would be down, 3-0, but this just presents another challenge for us. This team has had its back against the wall before and it responded so I just look at it as a huge challenge.