Novak works on arm strength after elbow procedure.
Three-time Grand Slam champion to headline field.
Fabio Fognini was the hero for Italy in its 3-1 victory over Japan.
Serena will face two major challenges in comeback says Chrissie Evert.
Novak Djkovic has had a medical "intervention" on his right elbow.
Australian Open boys' champion replaces Melbourne semifinalist in field.
The Williams' family dominance of SW19 could continue for years.
