WHITE PLAINS, N.Y.—Top-ranked Serena Williams is too wiped out to play in the Fed Cup against France on April 19-20, U.S. captain Mary Joe Fernandez said Wednesday.

"She is mentally and physically exhausted and needs a break, so bad timing for us, unfortunately," Fernandez said in a telephone interview. "But that happens sometimes. She's been going hard the past couple of years and needs to get refreshed."

Neither of the Williams sisters was on the roster submitted Wednesday by Fernandez for the upcoming World Group playoff, to be played on an indoor hard court at Saint Louis University.

"Serena and Venus both wanted to play," Fernandez said, "and I was looking forward to having them."

She called the 32nd-ranked Venus' absence the result of "an innocent mistake": According to Fernandez, Venus signed up for the hard-court tournament being played April 14-20 at Kuala Lumpur, Malaysia, not realizing that was the same week as the Fed Cup matches.

Without being able to rely on the sisters — who both have been ranked No. 1 and have a total of 24 Grand Slam singles titles, 17 by Serena — Fernandez picked a young roster that includes 18th-ranked Sloane Stephens, No. 42 Madison Keys, No. 49 Varvara Lepchenko and No. 57 Christina McHale.

"My team is gaining experience," Fernandez said. "I'm not sure who will play singles or doubles. We'll see how the practice week goes, and we'll go from there."

After losing at a tournament at Charleston, S.C., on April 1, Serena said: "I'm really just dead. I need some weeks off where I don't think about tennis and kind of regroup."

Fernandez said she spoke to Serena recently about pulling out of Fed Cup.

"Unfortunately, I guess Serena hit the wall after Charleston," Fernandez said.

"It's difficult for them because the priorities are the big tournaments. Hopefully we can get a (Fed Cup matchup) that's convenient (for) timing and geographically," she added.

French captain Amelie Mauresmo's players are No. 22 Alize Cornet, No. 74 Caroline Garcia, No. 76 Virginie Razzano and No. 87 Kristina Mladenovic.

The winning nation will enter the World Group in 2015 and compete for the Fed Cup title. The loser will drop down to World Group II.

The United States has won the Fed Cup 17 times, but not since 2000. France won it in 1997 and 2003.

"It's going to be tight," Fernandez said. "It's going to depend on those big points."