What is unclear is how long Iglesias will take up residence at Fenway Park. This could be a relatively short visit, depends on how well -- and how quickly -- third baseman Kevin Youkilis recovers from his ailing back.
To make room for Iglesias on the roster, the Red Sox optioned right-hander Junichi Tazawa to Triple-A Pawtucket.
With Youkilis unavailable for the third straight game, the Red Sox did not want to be left without a reserve infielder.
"With the playing conditions and with the roster situation, we didn't think it was fair for the team to play so short in the infield," said Red Sox manager Bobby Valentine. "We have a backup in case we need it."
Nick Punto again started in place of Youkilis at third.
The Red Sox will continue to monitor Youkilis in the short term before deciding if a DL stint is necessary.
"I can't tell," Valentine said. "I was with him today in the training room. There are times where it's pretty sore [with] different movements. He's doing everything he can in the training room. Yesterday it was during infield practice. The day before, it was during batting practice. He's doing everything he can. As far as other opinions or any of that stuff, I'm not sure where we are on it. It seems like he has a situation that we just have to get over."
If Youkilis did need to be shut down for a prolonged period, the Red Sox could start Iglesias at short and move Mike Aviles over to third. They could also send Iglesias back down and bring up another top prospect -- third baseman Will Middlebrooks.
Iglesias has been to Boston for temporary stints in the past. The expectation is that some day he will arrive for good as the team's everyday shortstop.
"It's a funny thing," Valentine said. "When you get to the big leagues, it's never ... it's not always how you plan for guys to be used. Sometimes guys get in, they never leave. Sometimes guys are planned to stay forever, and they're gone after two weeks. Let's say he's here and we'll use him. But it could be short."
Iglesias was in the running for Boston's starting shortstop position for most of Spring Training before losing the competition to Aviles.