The 28-year-old Russian beat Ukraine qualifier Illya Marchenko a 6-3, 6-3, 6-0 on Thursday on Show Court 2, which is No. 4 on the pecking order of show courts at Melbourne Park.
He doesn't have the profile of Roger Federer or Rafael Nadal, and he's never made a Grand Slam final, but Davydenko does have recent form on his side.
Former No. 1-ranked Ana Ivanovic has the profile, but no recent form to go with it. The 22-year-old Serb extended her run of poor results in a second-round 6-7 (6), 7-5, 6-4 loss to Gisela Dulko of Argentina.
Dulko was broken twice while serving for the match before finally breaking Ivanovic's serve _ helped by two double-faults from the 2008 French Open champion _ to clinch a place in the third round on her sixth match point.
Ivanovic, who lost the 2008 final here, has slipped to No. 21 in the rankings and didn't win a tournament in 2009. It was her first loss to Dulko in their three meetings.
In another early women's result, No. 10 Agnieszka Radwanska of Poland advanced 6-0, 6-2 over Russia's Alla Kudryavtseva.
Davydenko beat both top-ranked and No. 2 Nadal on his way to two titles in the last two months, including the Qatar Open this month where he saved two match points before a comeback win over Nadal in the final.
His best run at the Australian Open ended in a fourth-round loss in 2008. He did not play here last year due to a left heel injury, breaking a streak of 29 straight Grand Slam tournaments back to the 2001 U.S. Open.
If players progress according to their seedings, Davydenko would meet 15-time Grand Slam singles champion Federer in the quarterfinals here.
Federer was playing later on Thursday against Victor Hanescu of Romania.
Only seven matches into her comeback, Justine Henin held off fifth-ranked Elena Dementieva 7-5, 7-6 (6), winning the last three points of the tiebreaker to clinch a second-round victory worthy of a final on Wednesday night. She ended it on her second match point _ 24 minutes after she missed her first chance against the Olympic champion.
Henin, who retired in May 2008 while she was ranked No. 1, knows she's capable of reproducing the form that took her to seven major singles titles.
"I lived so much emotion on the court this evening. It was magical," she said. "I was afraid I wouldn't be able to do it, but it was the kind of situation I needed to re-find my confidence."