It's a good value signing. Martell was a solid, if unspectacular starter last season. While he didn't "explode", his per 36 numbers were up in almost all areas, and his FG% and 3FP% were both up - and he did this against other teams' starting small forwards. He's still only 21 and still has some "upside" - as shown in the brief flashes of incredible play he exhibited at times last season (that 24-point 3rd quarter against Utah was just flat out awesome). He looked great in that one preseason game, worked hard in the off season and came into camp in great shape.
We don't need a superstar at every position, and if Martell can be a solid, complimentary player at the starting small forward position, I think he's a good fit long term. With Oden in the low post, he should get plenty of open looks from the perimeter. He has that really sweet looking jumper, and when he shoots it with confidence, it goes in. He was still inconsistent last season, but again, he's still only 21. He has the mechanics on his shot down and the more he plays the more his confidence will grow. This contract extension by the Blazers gives him some security and should remove any doubts he may have about the team's commitment to him.
I hate to go all pop psychologist here, but given Martell's extremely rough childhood, I can't help but think some of his wavering self-confidence has to do with abandonment issues. By stepping up and signing him to an extension, KP has given him the reassurance that the team won't abandon him - of course, we could still trade him, but I don't even want to go there. I do think KP sees him as a long term part of this team - either as as starter, or a long range threat off the bench to spread the defense (a younger, more athletic James Jones).
BNM