Forgive Philip Rivers for not paying much attention to Danario Alexander when he arrived in the San Diego Chargers’ locker room late last October.

It was nothing personal, but Rivers had become used to seeing nameless receivers join the team during the season. After all, Rivers had to work with 17 different receivers during the 2010 season. After a while, they just became faces.

But it didn’t take long for Alexander to graduate from bottom-of-the-roster fodder to one of Rivers’ favorite targets.

“Honestly, I didn’t give him much of a thought right away,” Rivers said. “But that changed quickly.”

Alexander, who is 6-foot-5 and weighs 217 pounds, started making plays and turning the heads of players and coaches almost instantly.

“It went from 'Who is this guy' to 'How did we even get a chance to get him?' I couldn’t believe he came off the street. He should have been on a roster already,” Rivers said. “I thought he was an emergency guy, then it was 'Holy smokes, we need this guy. We got to get him on the field.'"

Remarkably, Alexander -- a star at Missouri who was ravaged by injuries in college -- was starting for San Diego at Cleveland in just his second week with the team and after just four practices.

Alexander made an instant impact and he kept it up. He had 37 catches for 658 yards (for an impressive 17.8 yard-per-catch average) and seven touchdowns in 10 games.

It is rare for players to make that type of impact after signing during the season. Rivers was right: Alexander, 24, was signed as an emergency player. But he became an integral part of San Diego’s offense, and he is part of the plan for the new brass.

The Chargers were worried that Alexander would get a contract offer in restricted free agency and leave the team. Rivers said he was “scared to death” Alexander would leave during the offseason. There was a lot of talk that some unnamed teams seriously considered inking Alexander to an offer sheet, but it never developed.

With Alexander under contract, San Diego plans to use him extensively. He will probably be in the front of the rotation along with Vincent Brown (who is back after a broken ankle wiped out his entire second season), Malcom Floyd and third-round pick Keenan Allen.

There will be a place for Alexander because of his size and raw skill. New coach Mike McCoy was not with the team when the Chargers struck gold with Alexander. But that doesn’t mean he isn’t thrilled to coach him.

“He showed the same thing this spring that we saw on tape when we took over,” McCoy said. “He has big-play capability. He has worked hard, and he has taken advantage of his opportunity here.”

Rivers said he has seen Alexander make strides this spring and expects him to be even stronger this season after having a full offseason and training camp with Rivers and the rest of the offense. Rivers and Alexander developed chemistry quickly last season. And Rivers said the two are still getting in sync.

Alexander is thrilled to get this opportunity after struggling with injuries. He was a highly rated prospect coming out of college. In 2009, he had 113 catches for 1,781 yards and 14 touchdowns.

However, Alexander couldn’t stay healthy. He tore his ACL twice in college and was hurt during the Senior Bowl leading up to the draft. He spent some time with the St. Louis Rams, but he didn’t make an impact. He had several workouts before catching on with the Chargers.

“Last year was really satisfying because of everything I went through,” Alexander said. “Staying healthy and getting a chance was a key for me. I know what happened last year never happens in the NFL. Guys usually don’t go from the street to a starter. But I had confidence in myself.”

Alexander hopes his career continues to soar, but he takes pride in turning heads when he arrived.

“They saw what I was doing with the ball after the catch in practice and all the guys said, 'Where did you come from?'" Alexander said. “They all went home and looked me up on the Internet. Guys wanted to know my history.”

Now, in San Diego, all they care about is Alexander’s future.