Hi gibbs_fan, welcome to WAT.
I'm not very clued up on Pakistan cricket myself so I can only speculate on possible reasons for the dropping of youngsters. However, I definately agree with you that Pakistan need an opener.
Imran Nazir looked quite good according to statisitics on Cricinfo, but the article that goes with it highlights his lack of technique and footwork. His poor performances in the Tests against Australia probably also worked against him, so that may be why he's not playing?
Taufeeq Umar (I assume that's who you meant?) has played 24 Tests for Pakistan, so has certainly been given an opportunity to prove himself. According to statisitics he looks pretty good too: an average of 40.73 does him no harm in my book. He did very well against Australia (top score 88) and South Africa (one of four Test tons: 135 his top score). He's also been included in
Pakistan's provisional 21-man squad to tour England this year.