BOSTONIts a relatively innocuous line in the Red Sox transactions, stuck in with a plethora of other moves: May 2 Will Middlebrooks recalled from Triple-A Pawtucket. Kevin Youkilis placed on the 15-day disabled list.Yes, Middlebrooks was called up to take Youkilis place while the veteran third baseman recovered from a low back strain. But what the rookie has done since then has made it impossible for the Red Sox to issue a return trip to Middlebrooks.The Sox 6-5 win over the Marlins Thursday night at Fenway Park was just the latest piece of evidence. Middlebrooks went 3-for-4 with a run scored and four RBI.With the Sox trailing by two runs in the eighth and Jarrod Saltalamacchia on second, Marlins right-hander Edward Mujica replaced Randy Choate. Middlebrooks was quickly behind in the count, 0-2, after two split-finger fastballs from Mujica. He took the next for a ball and fouled off another of Mujicas splitters. Mujicas fifth pitch, and first fastball, went for a ball. Then Middlebrooks jumped on the next pitch, a 94-mph fastball, crushing his eighth home run of the season into the bleacher seats in center field.The guy had a good split-finger, so I was just really trying to fight him off so I could get a good fastball to hit, Middlebrooks said.It feels awesome. If I can help us win at any point in time, Im happy.Ryan Kalish, Mike Aviles, and Daniel Nava combined to score the go-ahead run.Will was patient enough to get a pitch he could drive, said manager Bobby Valentine. He drove it for a terrific two-run hit.Taking those outside pitches, those sliders, splits, whichever they were, those were tough pitches and once he saw them early and swung at them, he recognized them later and took them. Thats when youre going good and when youre not chasing and you go back to the dugout.Hes a confident young guy. He doesnt get discouraged when he swings and misses.He didnt miss many in the three-game set with the Marlins. Middlebrooks went 6-for-8 with three runs scored, two two-run home runs, and seven RBI as his average rose from .289 to .316.It hasnt just been at the plate, either, where he has impressed. Middlebrooks made a nifty play on Jose Reyes to end the seventh.I thought that hop was going to make it all the way to me, Middlebrooks said. Took that step back so I could be ready to throw because hes a burner. Once I realized it wasnt I knew I had about a 20 percent chance of catching that ball. So just do or die and try to get them. It worked out.Its one of those where you just swipe at it and you got to get rid of it because he flies.Middlebrooks has been putting up numbers the Sox have not seen in a long time. He has hit safely in his last four games with a plate appearance, going 7-for-12 (.583) with a double, two home runs, three runs scored, and nine RBI.His performance against the Marlins Thursday gives him 31 RBI in 38 games this season. He is the first Sox batter to reach that mark since Walt Dropo had 34 RBI in his first 38 games, spanning 1949-50. Dropo, who died in December at 87, was the American League Rookie of the Year in 1950.Hes been outstanding since day one, said Cody Ross. Even the play that he made tonight. It was overlooked because of how well he swung the bat. But defensively, offensively just done everything that theyve asked him to. He deserves a lot of credit.Hes an impressive young man, Valentine said. I liked talking to him in spring training. I liked watching him and hes developing nicely. He comes out early and works on his defense. He crashed on that backhand play that he had to make that hes been working on with coach Jerry Royster. He made a real good defensive play. I love to see guys growing and learning and excelling at the same time. Its a perfect combination.But whats been a rather perplexing combination is finding equitable playing time for the veteran Youkilis and the rookie Middlebrooks. While Middlebrooks has appeared in 38 games, he has not started each of those games. He entered Wednesdays game as a pinch-runner for Youkilis in the sixth inning. With Youkilis return to health, and to the roster on May 22, Middlebrooks playing time has been less consistent.Thats a first for him in his career. But hes fine with it.It really hasnt been bad, he said. I knew that was going to be my role. So just try to accept it and play hard when my names called.I do the same thing every day whether Im playing or not, in the cage, on the field, groundballs. Everythings the same because anything could happen. He could get scratched. Anything could happen. So I just got to be ready.Its been Youkilis, Middlebrooks said, who has helped to make his adjustment to the big leagues easier.Hes been awesome. Middlebrooks said. Hes helped me out so much, man. Not just baseball, but off the field and how to handle everything.Still, with the way he is playing, its hard to keep Middlebrooks out of the lineup. But Valentine is content, for now, to keep things the way they are.It seems like hes doing just fine like this, Valentine said. Hes keeping sharp, hes watching and hes learning and when hes in there he doesnt look like hes missing a beat. Obviously.Meanwhile, Youkilis, who sat Thursday, is batting just .225 with a .359 slugging percentage and .311 on-base percentage, as his name gets churned through the trade rumor mill.Valentine acknowledged a players performance can affect his playing time.I think thats a fact of the game that we play."