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 | Arsenal | 34 | 24 | 5 | 5 | 82 | 26 | 56 | 77 |
| 2 | Manchester CityMan City | 33 | 23 | 7 | 3 | 80 | 32 | 48 | 76 |
| 3 | Liverpool | 34 | 22 | 8 | 4 | 75 | 34 | 41 | 74 |
| 4 | Aston Villa | 34 | 20 | 6 | 8 | 71 | 50 | 21 | 66 |
| 5 | Tottenham HotspurSpurs | 32 | 18 | 6 | 8 | 65 | 49 | 16 | 60 |
| 6 | Manchester UnitedMan Utd | 33 | 16 | 5 | 12 | 51 | 50 | 1 | 53 |
| 7 | Newcastle UnitedNewcastle | 33 | 15 | 5 | 13 | 69 | 54 | 15 | 50 |
| 8 | West Ham UnitedWest Ham | 34 | 13 | 9 | 12 | 54 | 63 | -9 | 48 |
| 9 | Chelsea | 32 | 13 | 8 | 11 | 61 | 57 | 4 | 47 |
| 10 | Bournemouth | 34 | 12 | 9 | 13 | 49 | 60 | -11 | 45 |
| 11 | Brighton & Hove AlbionBrighton | 33 | 11 | 11 | 11 | 52 | 54 | -2 | 44 |
| 12 | Wolverhampton WanderersWolves | 34 | 12 | 7 | 15 | 46 | 54 | -8 | 43 |
| 13 | Fulham | 34 | 12 | 6 | 16 | 50 | 54 | -4 | 42 |
| 14 | Crystal Palace | 34 | 10 | 9 | 15 | 44 | 56 | -12 | 39 |
| 15 | Brentford | 34 | 9 | 8 | 17 | 52 | 59 | -7 | 35 |
| 16 | Everton | 34 | 11 | 8 | 15 | 36 | 48 | -12 | 33 |
| 17 | Nottingham ForestNott'm Forest | 34 | 7 | 9 | 18 | 42 | 60 | -18 | 26 |
| 18 | Luton TownLuton | 34 | 6 | 7 | 21 | 47 | 75 | -28 | 25 |
| 19 | Burnley | 34 | 5 | 8 | 21 | 37 | 69 | -32 | 23 |
| 20 | Sheffield UnitedSheff Utd | 34 | 3 | 7 | 24 | 33 | 92 | -59 | 16 |
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