Davenport rebounded from a straight-set loss Saturday with a 6-1, 6-2 win over German Julia Goerges in 46 minutes and Harkleroad posted a a 6-4, 7-5 victory over Sabine Lisicki.
The former world No. 1 Davenport was originally scheduled to meet Tatjana Malek Monday.
"I just felt pressure more for my pride," said Davenport of her need to rebound from a lackluster performance on Saturday. "Normally I've played so well in Fed Cup. I felt really bad for my teammates. I really felt like that was one of my worst matches in a long time."
The round-of-eight match-up was pushed back to Monday after rain washed away Sunday's three-match schedule.
McPhee, Cokas 'working on their marriage' after affair
Duggar sisters unveil Christian dating rules in new book