ALAMEDA, Calif. — What looked to be a move of desperation is turning out to be one of Oakland Raiders general manager Reggie McKenzie’s most shrewd offseason acquisitions.

Having Donald Penn as their starting left tackle was never part of the Raiders’ plan. Yet Penn has been an anchor as well as the blind-side protector for quarterback Derek Carr for a Raiders offensive line that is coming off its best overall game in a 31-28 loss to the San Diego Chargers.

When Penn signed March 19, it was only after left tackle Jared Veldheer signed with the Arizona Cardinals and Rodger Saffold agreed to terms with the Raiders but failed his physical.

Meanwhile, Penn was released by the Tampa Bay Buccaneers, who thought his production in 2013 didn’t measure up to the $6 million he was scheduled to be paid in 2014.

The Raiders moved quickly to bring in Penn, who also visited the Washington Redskins.

The Redskins wanted him to play right tackle with Trent Williams entrenched on the left side, and to Penn, being moved to right tackle is the first step to being out of the league. At age 31, Penn believes he has some good years left on the left side.

“I’m not old, I’m young,” Penn said. “I’ve still got a lot left in me. I tangle with the best D-ends week in, week out and I’m going to continue to do that.”

According to Profootballfocus.com, Penn graded out higher than either Veldheer, the left tackle for the Cardinals, and Saffold, who returned to the Rams and was moved to guard.

That same service had Penn giving up 12 sacks last season. Although Penn acknowledges he didn’t have his best year, he thought that figure was high and he didn’t play as poorly as is widely believed.

“I didn’t have any luck,” Penn said. “Anything bad that could happen happened. If you really watch film, you can’t tell when a quarterback rolls into a sack when I’ve got my man blocked, or if I was trying to get to someone who came free.”

Offensive coordinator Greg Olson thought Penn, a Pro Bowl player as recently as 2012, could bounce back and gave his recommendation.

“I didn’t have a history with Donald like Greg did, but I had high expectations for Donald when we got him and he is playing even better than I anticipated at this point,” Raiders interim coach Tony Sparano said.

Sparano, who began the season as the Raiders line coach, has played a role in Penn’s bounce-back season.

“Even on days when I’m tired or dragging a little bit, Tony’s such a good coach he gets the work out of me,” Penn said. “He did a good job watching my film last year and getting me different tools to put in my tool box, making me a better player.”

Sparano likes Penn’s willingness to try new techniques.

“Sometimes you get veteran players and you’re trying to break bad habits and they’re stuck in their ways a little bit,” Sparano said. “Donald’s not like that. He’s an easy guy to coach.”