Again for Cubs, what to do at third base?

The Cubs are back to their age-old problem of groping for answers at third base.

By this time Josh Vitters should have been manning the hot corner for the Cubs.

The opening was there for him after Aramis Ramirez left as a free agent after nine highly productive years (2003-11), during which he hit 239 home runs and had an OPS of .887.

Ramirez was the most stable force at third base for the Cubs since Ron Santo was the mainstay from 1960-73, when he hit 342 homers and had an OPS of .826.

These days, the Cubs are mixing, matching and putting anybody they can find to play third.

In Tuesday night’s 9-8 loss at Philadelphia, Donnie Murphy became the sixth different player to start at third for the Cubs this year, joining Luis Valbuena, Cody Ransom, Brent Lillibridge, Steve Clevenger and Alberto Gonzalez.

The bright side is that Cubs third basemen have hit 17 home runs this season, compared with 12 all of last year, when the team trotted out Valbuena, Ian Stewart, Vitters, Joe Mather and Adrian Cardenas.

The Cubs are in a bind again because Valbuena went on the disabled list over the weekend and Ransom entered Wednesday in a 2-for-38 funk.

“We’re obviously trying to find some offense in that spot right now,” manager Dale Sveum told reporters in Philadelphia. “The defense has been incredible all season from Valbuena and Ransom.

“Right now, obviously, Ransom has had a rough stretch since the break, and we’re trying to find someone who has a hot bat.”

As creditably as they played at times, Valbuena and Ransom are veteran utility men who are not the long-term answer at third.

The Cubs could go temporarily with recently called up Junior Lake at third base; he came up through the minor leagues as an infielder. But Lake has replaced the traded Alfonso Soriano as the everyday left fielder, and Sveum seems inclined to leave it that way.

So what does the future hold? We’ll eliminate Lake for now, and we won’t speculate at this moment on players such as shortstop Starlin Castro or minor-league shortstop and phenom Javier Baez shifting positions.

Here are the top third-base possibilities in the minor leagues:

ŸMike Olt: Obtained from Texas in the deal that sent pitcher Matt Garza to the Rangers, Olt is trying to regain his stroke at the Cubs’ Class AAA Iowa affiliate.

Olt, who turns 25 on Aug. 24, is 7-for-54 (.130) with 1 homer for Iowa. He hit that homer Tuesday at Tacoma. With the Rangers’ Class AAA Round Rock club, Olt had a line of .213/.317/.422 with 11 homers and 32 RBI. He hit 28 homers last year with Class AA Frisco.

Olt suffered a concussion in winter ball and is battling back from vision problems. He still bears watching.

ŸVitters: The Cubs’ No. 1 draft choice in 2007, Vitters is on the disabled list at Iowa, where he has played just 26 games this year. A quadriceps injury early in spring training derailed the early part of the season.

The Cubs called Vitters up to the big leagues last August, and things did not go well. He had a batting line of .121/.193/.202 with 2 homers. The Cubs also did not seem pleased with his work in the field.

It could be that Vitters has gone from “prospect” to “suspect” in the new regime’s eyes.

ŸChristian Villanueva: In last year’s trade with Texas for Ryan Dempster, the Cubs got pitcher Kyle Hendricks and Villanueva. Hendricks just moved up from Class AA Tennessee to Iowa, where he will start Thursday night.

Villanueva, 22, entered Wednesday with a line of .260/.311/.446 for an OPS of .756 at Tennessee. He had 14 homers, 54 RBI, 24 walks and 95 strikeouts in 443 plate appearances. He had made 19 errors.

Two years ago at Class A Hickory, Villanueva hit 17 homers and stole 32 bases.

Villanueva is on the 40-man roster, and if the Cubs were in a real bind, they could recall him without costing someone a roster spot. If he can get the OPS over .800, he really could be an intriguing prospect.

ŸKris Bryant: The 21-year-old Bryant has just begun his pro career after the Cubs took him with the overall second pick in June.

In 13 games at short-season Boise (A), Bryant is 14-for-48 and has an overall line of .292/.352/.583 with 5 doubles, 3 doubles and 11 RBI.

Bryant hit 31 home runs for the University of San Diego this past season and led the nation in walks and slugging percentage.

There’s no rush on Bryant. It’s possible he will move up to high-A Daytona before the summer is over.

ŸFollow Bruce’s Cubs and baseball reports via Twitter@BruceMiles2112, and check out his Chicago’s Inside Pitch blog at dailyherald.com.