ARLINGTON, Texas — When the Red Sox outbid the New York Mets last December for shortstop Julio Lugo, they did so believing that they were getting an offensively skilled shortstop who could bring some athleticism to the top of their batting order.

To date, Lugo has not been the offensive force the Sox envisioned. As the Sox took on the Texas Rangers in the middle game of their weekend series here last night, Lugo was batting a mere .235 and his on-base percentage was a disappointing .294.

But by other measures, Lugo has been a dynamic fit in the Boston lineup. His 29 RBI placed him third on the team behind only Mike Lowell (37) and David Ortiz (38) and ahead of cleanup hitter Manny Ramirez (28).

His RBI total, in fact, represented the most for any leadoff hitter in the American League. In all of baseball, only Atlanta’s leadoff hitter Kelly Johnson had as many RBI.

Lugo is on a pace for exactly 100 RBI this season, easily outstripping his previous single-season high of 75 set in 2004 with Tampa Bay.

“Evidently,” said manager Terry Francona, “he’s getting the hits when they mean the most.”

Lugo was hitting .319 with runners in scoring position, some 83 points higher than his regular batting average. “He’s always been a good hitter,” said teammate Alex Cora. “I think maybe he’s concentrating a little better with runners in scoring position. It’s a great addition for us, to be able to turn that lineup over and produce runs from that spot.”

Of course, part of the secret of Lugo’s production has been the ability of the lower part of the order to reach base. From the ninth spot in the lineup — usually filled by Cora or Dustin Pedroia — the Sox had compiled a .379 on-base percentage, easily the best in the American League. Next closest was Tampa Bay, with a .331 OBP.

“When you come up with men in scoring position,” said Lugo, “you want to produce. I mean, I want to get a hit every time up, you know? But especially (with runners on). It helps to have good guys in front of me. (Cora and Pedroia) get on base all the time.”

Francona is fond of saying that the Red Sox’ offensive strategy is rooted in their desire to “keep the line moving, that is, to produce big innings, wear down opponents and get into the other team’s bullpen early.”

“He never looks to do too much,” said Cora, “and that’s the key.”

In Lugo, the Sox have found another weapon for that approach, albeit from a somewhat unlikely source.

“People think batting average is important,” said Lugo, “because baseball is a game of numbers. I’m not focusing on that. I want to get guys across (the plate). Producing for your team is the most important thing in baseball. Obviously, I’m not happy with my average. But we’ll see where it is in September.”

Lugo entered the year with a career .277 average and a lifetime OBP of .340. If he could approximate those numbers by the end of the season, while maintaining his run-producing ability, the Sox would be more than satisfied.

If Lugo’s run production has been something of a surprise, his contributions elsewhere were more expected. Lugo ranks among the team leaders in two other significant categories for leadoff men: runs scored and stolen bases.

His 26 runs scored ranked him tied for third on the Sox and his 14 stolen bases lead the team, five ahead of Coco Crisp. Lugo has yet to be thrown out stealing

The 14 steals without being caught were the most of anyone in baseball. Los Angeles Angels of Anaheim rookie outfielder Reggie Willits was next with 11-for-11.

Lugo’s 14-for-14 start on the basepath ties a Red Sox record. Leon Culbertson was successful in all 14 of his stolen base tries in 1943.

At that pace, Lugo seems likely to establish another career-high. He stole 39 bases with the Devil Rays in 2005. Only one other time — last season when he stole 24 with the Devil Rays and Dodgers — has Lugo accumulated more than 22 steals.