He had forced his way into the New Zealand squad in March ahead of the home series against Australia, whereas Blundell had been in the frame since last December.
With work still to do on living a near-fulltime athlete's lifestyle, Blundell had been "followed around" by injury and the selectors' concerns were that as a pace bowler he might not last the distance in Dubai, Raj said.
"He's definitely up there with the skill set, it's about keeping him on the park."
The door is not completely shut on Blundell, who Raj understands remainsat the head of the list for the standby bowlers.
He will play Hawke Cup cricket in January and try to force his way into the Central Districts A side, who will play a tournament against the other association's A teams as well as against the New Zealand Under-19 squad as part of their World Cup warm-up.
Raj said he could still get that plane ticket because should New Zealand advance to the quarter-final and semifinal stage, the heat of Dubai made it likely one of the bowlers would break down.
"Very slim to make the [final] 15, but his chances of getting called over are very high," he said.
"That's why he needs to keep up with his skills."
Collier made two decent scores including a century against Northern Territory teams in July when the New Zealand Under-19 toured Australia for a tri-series with the Aussies and World Cup hosts India.
At Hawke Cup level, he was the most consistent batsman for Wanganui of those who played all three games, but was frustrated as he made slow but steady beginnings to his innings, then fell when he was poised to crack on for a big score.
The New Zealand team will departfor the Under-19 World Cup in late January.
Meanwhile, today's final round of the Porter Hire Premier 1 one-day competition has the crucial match between Property Brokers United and Matt Burke Engineering Marton Saracens at Victoria Park.
Defending champions United lead the competition, so victory will secure the title and set them up to play the Taranaki one-day champions next weekend.
Beaten by 47 runs in their first meeting in early November, Saracens need to win in impressive fashion to claim the championship on run rate.