The third baseman, who was sidelined with back problems, went 0-for-3 in Pawtucket on Saturday, but had a .333 average with two home runs and six RBIs in his first four games in Triple-A.
"Another game last night where there was more timing, good swings, but yet not the results that he's had," Farrell said. "I want to go back to when we outlined this -- this wasn't a matter of a batting average to get him back here. It was a matter of getting back into the flow of a game and gaining some momentum. We're hopeful to see him soon."
Iglesias, who's been the primary replacement at third, has made the most of the absence. He had two more hits on Saturday to raise his average .443 on the year in 70 at-bats entering play Sunday.
When Middlebrooks is called up, the Red Sox will have to make a roster move. The decision will likely come down to either demoting Iglesias or utility man Pedro Ciriaco, who has not played much recently and is out of options.
Farrell insists Iglesias' hot hitting has no bearing on when Middlebrooks is called up, however.
"Will's our third baseman," he said. "We've said that. But yet at the same time, Jose is doing an excellent job, and once Will's returned and the roster decision is made, if the scenario is that Jose is our utility guy, we've got to be sure that we rotate him through there to keep him in the mix."
That being said, if Iglesias is still on the roster when Middlebrooks returns, Farrell isn't afraid to ride the hot bat even if that means giving Iglesias some starts at third.
"We have to stay flexible," Farrell said. "That's what internal competition is about. It drives everyone to be better. You don't want to stunt that. You don't want to take away from that or get in the way of it."
Michael Periatt is an associate reporter for MLB.com. Follow him on Twitter @Michael Periatt. This story was not subject to the approval of Major League Baseball or its clubs.