The Braves shortstop returned to the lineup on Saturday for the first time since Aug. 22, but Cox didn't want to assure Renteria playing time Sunday -- a day game after a night game -- until Renteria tested the ankle.
Renteria initially injured the ankle trying to field a ground ball against Houston at Turner Field on Aug. 2. He landed on the disabled list the next day, and tried to return on Aug. 22 at Cincinnati.
But Renteria re-injured the ankle in his first plate appearance on a check swing. His return on Saturday impressed Cox, who seems to be running out of superlatives to describe Renteria's season.
The 32-year-old native of Colombia had two hits and two hard-hit balls that were caught. Entering Sunday's game, Renteria's batting average sits at .337, second only to Philadelphia's Chase Utley.
"He hit four bullets," Cox said. "The ball he hit hardest was to center -- that was a lineout right against the wall. It's amazing."
Renteria easily made it through his brief workout on Sunday. The only thing that gave him trouble was the brace he must wear. For someone who rarely gets hurt, every aspect of an injury is an inconvenience.
"I hate this thing," he said.
Sunday's lineup includes Kelly Johnson batting eighth and playing second base. Rookie Yunel Escobar, who filled in while Renteria was hurt, will be back in a platoon role at second with Johnson, and was out of the lineup on Sunday.
Carlyle it is: Cox announced on Sunday that Buddy Carlyle will make the start on Tuesday in New York against the Mets. Cox waited to see if Carlyle or rookie Jo-Jo Reyes would be needed in relief during the series against Washington.
"[I wanted to] see how these games went," Cox said. "If we had to use Buddy to help win, or Jo-Jo, the other guys would start. It's that time of year."
Carlyle lasted just 1 2/3 innings and threw 45 pitches against Philadelphia on Tuesday after allowing three runs. He appeared upset when Cox took him out, and Reyes pitched well in relief.
Cox said Reyes could be used again in relief if Carlyle struggles.
Organizational update: The Triple-A Richmond Braves advanced to the International League championship series, known as the Governors' Cup, with a 4-3 win over the Scranton/Wilkes-Barre Yankees on Saturday.
Iker Franco delivered the game-tying single and Derrick Arnold, who spent the regular season with Class A Myrtle Beach, won it with a sacrifice fly to center field. Arnold was promoted to Richmond on Tuesday.
"Any day you come to the ballpark, you hope you could be that one person to change the game," Arnold, told minorleaguebaseball.com. "When I woke up this morning, I didn't think I was even going to get to play.
"I just got up here a week ago, but I never thought once I'd come in today and win the game. Any time you get a chance to do something like that, it's unbelievable."
Oregon-izational update: Another Braves Minor Leaguer had a big day on Saturday, but it didn't come in a baseball uniform.
University of Oregon quarterback Dennis Dixon, a fifth-round pick of the Braves in June's First Year Player Draft, led the Ducks to a 39-7 win over Michigan. Dixon passed for 292 yards with three touchdowns and he rushed for another score.
With Bradenton of the Gulf Coast League and Danville of the Appalachian League, Dixon combined to hit just .176 (13 for 74). He has led the Ducks to a 2-0 record to start the season.
Franco missing: Julio Franco injured his hamstring during the series with the Phillies earlier this week and has not been in uniform this weekend against the Nationals. The origin of the injury is unknown.
Franco has been in the Braves' clubhouse, but rarely seen because he is often getting treatment. He last played on Sept. 2, making a pinch-hitting appearance. Franco accepted an assignment to the Minors after Atlanta acquired Mark Teixeira on July 31. Since re-joining the Braves on Sept. 1, Franco has just two at-bats.
Chuck and duck: Chuck James probably saw his life flash before his eyes when Washington second baseman Ronnie Belliard hit a smash up the middle during the fifth inning of James' start on Saturday.
James managed to snag the liner, but by no fault of his own. It happened to hit James' glove, which was extended towards third base on the pitcher's follow-through.
"As long as they're hitting them, I'll throw [my glove] out there anyway and hope for the best," James said. "I see that play all the time on TV, and I'm like, 'I probably have no shot if they hit one back like that.' It was nice to finally make one."
Coming up: The Braves start a three-game series at Shea Stadium against the Mets on Monday night at 7:10 p.m. ET. Atlanta sends Tim Hudson (15-7, 3.47 ERA) to the mound to face left-hander Oliver Perez (13-9, 3.46).