The Knicks should play to win. Tanking does not guarantee a top 5 pick. Remember last year? The Knicks only won 23 games, and who got the #1 pick? The 33-49 Chicago Bulls. The Knicks need to just be as competitive as they can. As hard as it may seem to believe, there are plenty of quality players that can be drafted, even with the 10th, 15th, or 20th overall pick.
Examples: 10th overall-Brook Lopez(2008), 14th overall-Al Thornton(2007), 17th overall Danny Granger(2005), 15th overall Al Jefferson(2004), 18th overall David West(2003), 10th overall Caron Butler(2002), 19th overall-Zach Randolph(2001)
I do not feel the Knicks have any shot at making the playoffs this year, because they do not have enough talent to consistently win games, but that does not mean that the Knicks have to lose all of their games on purpose.