The Bolton Wanderers defender has been locked in discussions with officials from Chelsea over the last two weeks.
It looked for a while that the deal may fall through, but Villas-Boas expects to have the England international at his disposal "soon".
"Gary passed his medical and should be our player soon," the Chelsea boss told reporters.
Cahill is thought to be costing Chelsea around £7m.
Restore Data
| Team | P | W | D | L | F | A | GD | PTS | |
| 1 | Manchester CityMan City | 4 | 4 | 0 | 0 | 11 | 3 | 8 | 12 |
| 2 | Arsenal | 4 | 3 | 1 | 0 | 6 | 1 | 5 | 10 |
| 3 | Newcastle UnitedNewcastle | 4 | 3 | 1 | 0 | 6 | 3 | 3 | 10 |
| 4 | Liverpool | 4 | 3 | 0 | 1 | 7 | 1 | 6 | 9 |
| 5 | Aston Villa | 4 | 3 | 0 | 1 | 7 | 6 | 1 | 9 |
| 6 | Brighton & Hove AlbionBrighton | 4 | 2 | 2 | 0 | 6 | 2 | 4 | 8 |
| 7 | Nottingham ForestNott'm Forest | 4 | 2 | 2 | 0 | 4 | 2 | 2 | 8 |
| 8 | Chelsea | 4 | 2 | 1 | 1 | 8 | 5 | 3 | 7 |
| 9 | Brentford | 4 | 2 | 0 | 2 | 6 | 6 | 0 | 6 |
| 10 | Manchester UnitedMan Utd | 4 | 2 | 0 | 2 | 5 | 5 | 0 | 6 |
| 11 | Bournemouth | 4 | 1 | 2 | 1 | 5 | 5 | 0 | 5 |
| 12 | Fulham | 4 | 1 | 2 | 1 | 4 | 4 | 0 | 5 |
| 13 | Tottenham HotspurSpurs | 4 | 1 | 1 | 2 | 6 | 4 | 2 | 4 |
| 14 | West Ham UnitedWest Ham | 4 | 1 | 1 | 2 | 5 | 6 | -1 | 4 |
| 15 | Leicester CityLeicester | 4 | 0 | 2 | 2 | 5 | 7 | -2 | 2 |
| 16 | Crystal Palace | 4 | 0 | 2 | 2 | 4 | 7 | -3 | 2 |
| 17 | Ipswich TownIpswich | 4 | 0 | 2 | 2 | 2 | 7 | -5 | 2 |
| 18 | Wolverhampton WanderersWolves | 4 | 0 | 1 | 3 | 4 | 11 | -7 | 1 |
| 19 | Southampton | 4 | 0 | 0 | 4 | 1 | 8 | -7 | 0 |
| 20 | Everton | 4 | 0 | 0 | 4 | 4 | 13 | -9 | 0 |
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