Andy Levitre is a left guard for the Tennessee Titans.

Andy Levitre hasn’t earned All-Pro or Pro Bowl honors in his five-year career.

Andy Levitre signed a six-year, $46.8 million contract with $13 million guaranteed last year.

Andy Levitre is one reason it might be difficult for the 49ers to sign left guard Mike Iupati to a contract extension.

Iupati, of course, is one of four prominent Niners who are entering the final year of their contract in 2014. The No. 17 pick in the 2010 draft, Iupati was a first-team All-Pro in 2012 who has earned Pro Bowl honors the past two seasons.

Iupati is generally regarded as superior to Levitre, meaning his agent will likely contend he merits a superior contract. That would mean an asking price of somewhere north of $8 million a season.

If, indeed, that’s an accurate ballpark figure, here’s a few reasons why it’s hard to envision the 49ers making an extension for Iupati an offseason priority:

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As a guard, Iupati would be more easily replaced than the 49ers’ other big-money, contract-extension candidates: quarterback Colin Kaepernick, outside linebacker Aldon Smith and wide receiver Michael Crabtree.

The general belief that guards aren’t a high-priority position is reflected in the draft: Only eight guards have been selected in the first round since 2000, according to ProFootballReference.com.

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It could be argued Iupati is an exception to the above rule. (In fact, I made this argument here last year).

Iupati is one of three guards selected with a top-20 pick since 2002 and his rare blend of size (6-foot-5, 331 pounds) and agility is what put him in select company. In 2012, general manager Trent Baalke, who drafted Iupati, said he falls into the rare-bird category.

“I don’t know that (Iupati) is a once-in-a-generation player, but he’s certainly not an every-year guy,” Baalke said. “You just don’t find men that big; that move that well; that are that powerful on a consistent basis year in and year out.”

That said, Iupati’s 2013 season doesn’t provide him with maximum negotiating power. After making 58 straight starts to open his career, he missed four games with a knee injury, sustained a broken ankle in the NFC Championship Game and was inconsistent in pass protection, possibly because of a nagging shoulder injury.

If the 49ers don’t make an enticing extension offer, it’s possible Iupati, who will earn a $2.77 million base salary in 2014, will be content to hit the open market after a stronger season in 2014.

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As former NFL agent Joel Corry (@corryjoel) notes, there is also the matter of left tackle Joe Staley, who signed a six-year, $43.2 million extension in 2009. Staley, who has made three straight Pro Bowls, has outperformed his contract.

“In the typical offensive-line hierarchy, your left tackle is your highest-paid player,” said Corry, who writes for CBS Sports and the National Football Post. “They extended Joe Staley in 2009 after two years of service and that deal hasn’t quite kept pace with the market. So is a guard going to be paid more than your left tackle? Extending Iupati, I really think that’s a challenging one right there.”

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Given the other areas that need to be addressed, the 49ers might be done pouring big money into their offensive line after they signed right tackle Anthony Davis to a five-year, $37.3 million extension last year.

Right guard Alex Boone is signed through 2015 and backup Daniel Kilgore, a 2011 fifth-round pick, could be the heir apparent to free-agent center Jonathan Goodwin. Guard Joe Looney, a 2012 fourth-round pick, has scant experience, but he filled in capably for three-plus quarters in a home game against the Rams this past season.

Looney, who slipped in the draft two years ago because of a foot injury, could be the future replacement for Iupati. He doesn’t have Iupati’s pedigree, but his 2015 base salary ($660,000) will likely be a fraction of what Iupati commands if he hits the open market.