CHICAGO (AP) — Addison Russell started on the bag, then then moved behind the base and finally ended up in front for a couple more throws. Then it was his turn to feed Starlin Castro, and he gracefully fielded each grounder before making an assortment of flips to the shortstop coming across second.

Each nimble step had a purpose. Every throw was on target. Not bad at all for a rookie learning how to play second base with the Chicago Cubs.

"I feel pretty comfortable at second," Russell said. "You know I'm turning a lot more double plays more smoothly, also just making routine ground balls as well. That builds my confidence."

Before Russell was promoted to the Cubs in April, the sum total of his professional experience at second was five starts at Triple-A Iowa. He was a high school shortstop when Oakland selected him with the No. 11 pick in the 2012 draft, and he played the same position in the minors while developing into one of baseball's top prospects.

But the Cubs have Castro at shortstop, and they wanted Russell's bat in the lineup right now. So they decided to try the 21-year-old Russell at second.

"I think he's done a very nice job," infield coach Gary Jones said. "I mean, it's tough making that switch at this level. Basically, you think about it, he had never really played second base. Played four or five games in Triple-A, and then boom, he was here."

Russell has a string of 12 consecutive games without an error heading into this weekend's series at St. Louis. He started Thursday's 4-0 loss to Los Angeles at shortstop, and then returned to second when Castro entered in the sixth.

Manager Joe Maddon said he thinks Russell will be a starting shortstop down the road, but his progress at second has been impressive.

"There was so many uncomfortable moments, and now he looks like he's been doing it for several years," Maddon said. "He really has, but he does have that potential and that ability to be a major league shortstop, too."

Russell really showed off his increased comfort at second in Tuesday night's 1-0 victory over Los Angeles, robbing Joc Pederson of a hit with a leaping grab and also making a nice play on a grounder by Jimmy Rollins.

"The angle in general I think is just completely different," Russell said, highlighting the most difficult aspects of the transition to second, "especially whenever you field the ground ball and also you're trying to make the throw. First base is a little bit more behind you than it is at shortstop.

"Just reading the ball off the bat in general was pretty tough and also some of the footwork stuff whenever you turn double plays was kind of difficult, too. But the more familiar I get with second base, the more easier it is."

The shortstop is often the best athlete on the team in prep and college ball, so it's not unusual to see converted shortstops at other positions in the big leagues. Red Sox second baseman Dustin Pedroia played shortstop in college at Arizona State, and Stephen Drew was a slick-fielding shortstop for his entire career before he spent some time at second with the Yankees last year.

But making the transition in the majors at such a young age is a more unique situation.

When Brandon Phillips made his debut with Cleveland in 2002, the Indians had Omar Vizquel at shortstop. So Phillips went over to second.

"Playing in the big leagues, that was my first time ever at second base, playing next to one of the greatest shortstops to ever play this game," Phillips said. "I felt kind of lopsided being over there at second base."

Phillips said his new position began to feel more natural when he was traded to Cincinnati in 2006 and then-Reds manager Jerry Narron told him to just be himself in the field. Four Gold Gloves later, Phillips is regarded as one of the majors' best defensive second basemen.

"I feel like second base is way easier than playing shortstop," Phillips said. "I think a lot of people say the hardest thing about playing second base is turning the double play. That really wasn't hard for me. It was just the fact of not letting the ball play you."

For Russell, the education continues while the Cubs try to keep up with the Cardinals and Pirates in the rugged NL Central. Jones said there are still things that come up during the course of a game that the two will go over, but he has been impressed with Russell's ability and work ethic.

With the Cubs in the middle of a tough stretch of games, Jones has tried to back off a bit. But Russell had Jones hit some extra ground balls to him before facing the Dodgers on Tuesday.

"He definitely wants to be good, and that's the reason he is good," Jones said.

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AP Sports Writer Will Graves in Pittsburgh contributed to this report.

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Jay Cohen can be reached at http://www.twitter.com/jcohenap