Yes, need is a factor, but you don't have needs at just one position. You look at the entire roster holistically and try to get the maximum talent possible that will benefit the teams performance. You may be able to plug a hole at cornerback, but is there a more talented wide receiver available that would make your team more explosive on offense? Even though you may have good wide receivers, you can take the wide receiver because he is much better than the cornerback, and what you have done in that case is to increase the overall talent on your team. Now you still need to address the deficiency on your defense but there are much more efficient ways to do it without compromising the talent on your roster.
