The D-backs made acquiring a second baseman their top priority this winter with the departure of free agent Orlando Hudson, who started for them from 2006-08.
"Felipe is a great fit for our club," D-backs GM Josh Byrnes said. "Obviously, we were hoping to address second base this offseason. He can do a lot to complement our roster defensively, with his baserunning and what he can do offensively."
Lopez was not the first person the D-backs looked to at second, but he does have the most potential. Arizona made a one-year offer, with a club option, to Ramon Vazquez and when they were rebuffed, they made a one-year offer to Mark Loretta, who signed with the Dodgers.
Both of those players lacked the athleticism of Lopez, who is entering the prime age range for a player.
"At the beginning of the Winter Meetings, I didn't think this caliber of player would be available to us," D-backs manager Bob Melvin said. "So, obviously, I'm probably the most excited person here."
The 2008 season was a Jekyll and Hyde one for Lopez, who hit just .234 for the Nationals before being released on July 31. Less than a week later, the Cardinals signed him, and he hit .385 for them.
"I wasn't getting a lot of playing time over there in Washington, it just wasn't a good fit," Lopez said. "They're still trying to figure things out, and I was just not the right fit for that time. I think it was a good thing for them to let me go, because they were kind of holding me back. When I went to St. Louis, I could show what I was able to do."
Lopez's best season was with the Reds in 2005, when he hit .291 with 23 homers and 85 RBIs. That earned him a spot on the National League All-Star team.
"I'm very capable of repeating that in Arizona," he said. "It's all about getting playing time and playing hard, and the talent will show itself."
Lopez will be the everyday second baseman and may even find himself at the top of the batting order, if Melvin decides he wants to move Stephen Drew down into more of a run-producing spot.
"Actually, he can hit just about anywhere, and that just adds to the versatility of the player," Melvin said. "Certainly gives me an option in the leadoff spot. He's hit there before. I'd like to talk to Felipe before I commit to which spot."
When he does speak with Lopez about it, he will find a flexible player.
"It's up to the manager," Lopez said. "I can hit wherever, I don't care. I know my role, and I know what I have to do at the plate -- get on base and steal bases."
Up until last season, Lopez was primarily a shortstop. He has also played second, first and third, as well as left and right field during his career.
"As a shortstop, you have the luxury of being athletic enough to play other positions," he said. "I'm very comfortable [at second base]."
Ironically, Lopez was part of Hudson's wedding party last month, and he got a scouting report on the D-backs from his close friend.
"He spoke highly of the Diamondbacks and everybody in the front office and coaching staff," Lopez said. "He had a lot of good stuff to say. It's kind of a no-brainer. This team is young and has a lot of positive stuff going on."