Weeks' .769 OPS over the past four seasons ranks eighth among Major League second basemen with at least 1,000 plate appearances in that span, behind the likes of Robinson Cano and Dustin Pedroia, but ahead of the Reds' Brandon Phillips and the Angels' Howie Kendrick. But after consecutive years of 20-plus home runs in 2010 and '11, Weeks has endured consecutive subpar seasons, batting .209 in '13 with a .306 on-base percentage and a .357 slugging percentage before undergoing surgery this month for a torn left hamstring.
The injury opened playing time for Gennett, who entered Thursday's start in the leadoff hole hitting .321/.358/.527 while playing adequate defense, the area in which Gennett needed the most work in his Minor League development.
"I think he's been really good," Roenicke said. "He's going to need some time, probably, to figure out the timing of plays; fast runner, slow runner, just when he needs to hurry it up and when he needs to slow it down. That usually comes with experience.
"Besides that, I think he's been really good. He's turned double plays really well; the play we saw [Wednesday] night, diving for the ball and getting up and throwing, he's done a really nice job."
That play actually occurred in right field. Positioned in the outfield as part of a defensive shift against power-hitting Pedro Alvarez, Gennett dove toward center field for a grounder and threw out Alvarez at first base.
"I like diving around, making awkward throws," Gennett said. "Sometimes those are the ones where I get off the most accurate throw, when I'm not even looking at the base. [Wednesday's] was one of those plays where I was just happy to stop the ball and save a run, but if we can get the out, it's the cherry on top."
Gennett has focused several years on his defense, working with roving infield instructor Bob Miscik. Fielding and throwing were never the issue, he insisted, but he has worked to make better split-second decisions.
"When to make a big play, when to just 'eat' the play," Gennett said. "There are times when you should make a big play and times when you shouldn't, because you [risk] making a long inning even longer. For me, if I mess up, it's going to happen, but I try not to do the same thing twice."
Has the Major League game moved fast for him?
"It is if you let it," Gennett said. "For me, if I'm in the game I know what pitch is coming and I know what the batter is going to do with it, and that slows the game down a little bit. If you're just out there getting surprised all the time, it must be tough."
Gennett won't turn 24 until May, and he has Minor League options remaining. Weeks will be 31 next month and will earn $11 million in 2014, the final guaranteed season of his four-year, $38.5 million contract. Weeks also has an $11.5 million vesting option for '15 that will become guaranteed if he is healthy at end of '14, and he has 600 plate appearances next year, or 1,200 plate appearances in '13-14 combined.