The consensus feeling was that Star Lotulelei, while the #1 DT prospect in the draft, was not a threat to russ the passer. This view is supported by his only getting 7 sacks in 38 games at Utah. (Compare this to 6 sacks in 24 games - only 11 of them starts - for Sheldon Richardson.) This probably played a role in Lotulelei's sliding down the draft board, as he was likely not viewed as a coveted "3 down DT" who could stay on the field in the passing-heavy NFL. (Then again, it might have been just how the board went, as lots of other DTs dropped also, including Shariff Floyd to 25 and Johnathan Hankins, Kawann Short and Jesse Williams out of the first entirely. Looks like the run was on OLs, even interior OLs, and DEs.)
But I am thinking that the consensus may be wrong, and Lotulelei may indeed develop to be a pocket collapser and pass rusher in Carolina. Here is why: Lotulelei did not put up statistics that reflected his ability because he was playing for a glorified mid-major in Utah. Had Utah remained a mid-major, Lotulelei would have played against mid-major offensive lines and dominated. But instead, the season that Lotulelei became a full time starter at Utah, his Utes moved from the Mountain West Conference to major college play in the Pac-12. So Lotulelei was on a mid-major caliber defensive line but being blocked by BCS conference caliber offensive lines. Because of this, Lotulelei faced "consistent double- and even occasional triple-team blocks." Well with Johnson and Hardy on the outside, Edwards next to him and 3 great LBs behind him, those double and triple team blocks won't be nearly as consistent!
Another reason: mid-major program means mid-major position coaching. Translation: Lotulelei is still raw. Again from Sportsline: "On the field, he battles consistency. Relies too much on his unique physical traits to overcome rather marginal technique. Does not possess an elaborate array of pass rush moves ... too often is stale-mated when his initial burst and power are contained." Well who better to fix those issues than Carolina DL coach Eric Washington, who specializes in DTs? He will teach Lotulelei consistency of effort, technique and pass rush moves in short order.
Look at it this way. If Lotulelei was able to consistently dominate major college competition while playing with mid-major teammates despite not having good technique or proper pass rushing moves, imagine what is possible when he is well coached and is playing around some of the better front seven talent in the NFL? So the answer that question is YES, Star Lotulelei can develop into a pass rushing threat. And that is precisely why the Panthers were so glad to get him.