Signed to a four-year major league contract worth $8.25 million in 2009, Iglesias is a tremendous defensive shortstop, worthy of winning Gold Gloves if he plays regularly. His range, hands, and arm strength all rate as excellent, and scouts love his instincts and quick reactions. He'll make occasional errors (five already in 24 games for Triple-A Pawtucket this year), but he also gets to balls that most infielders can't reach according to scouts, and range is more important than reliability for a young infielder. Reliability usually improves over time; range doesn't.
The main problem for Iglesias is offense. He has some bat speed, and the Red Sox insist that his excellent hand-eye coordination will eventually translate into good hitting, at least for average. He did hit .285 in 57 games in Double-A last year. But he has almost no power, was hitting just .253/.278/.253 this year in 24 games for Pawtucket (zero extra-base hits in 92 plate appearances), and is hampered by poor strike zone judgment. He runs well but doesn't steal many bases. Without significant improvement with his plate discipline and/or power, his offense will consist entirely of an empty batting average.
Iglesias is just 21 years old and is still adapting to North America, so there is still a chance his offense will improve. His glove will keep him employed for a long time. Right now he needs at-bats to work out the kinks in his hitting. He won't get a lot of them in Boston right now as long as Jed Lowrie is hitting, so expect Iglesias to return to Triple-A once Scutaro is healed.