Second-placed Orient are expecting a sell-out for the crunch League One clash with Mark Warburton's side at Brisbane Road.
Orient stretched their unbeaten run to five games with a 2-0 win over Port Vale on Tuesday and have now won four of their last five matches to enhance their chances of securing automatic promotion.
Brentford are just a point behind them after securing back-to-back victories over Bradford City and Tranmere Rovers and Orient boss Slade knows how much is at stake when the two sides lock horns this weekend.
He said: "It's vital, but it doesn't matter who we're playing. It happens to be Brentford. It would be vital if it was anyone else in the league.
"It's going to be a tough game because they’re a very good side. Their record stands up.
"If we could take three points of them it would be fantastic, it would give us a little bit more momentum and put them under pressure."
Free-scoring Wolves look destined for an immediate return to the Championship after securing a club record ninth consecutive win at Swindon Town on Tuesday.
The leaders won 4-1 at the County Ground to stay two points clear of Orient and will fancy their chances of stretching their winning streak to double figures when they entertain relegation-threatened Shrewsbury Town on Saturday.
Preston North End will attempt to half FA Cup semi-finalists Sheffield United's 10-game winning run when Nigel Clough's side travel to Deepdale on Monday.
At the other end of the table, beleaguered Notts County can ill afford to slip up again when they travel to fellow strugglers Tranmere.
A 3-1 home defeat against MK Dons on Tuesday ensured Shaun Derry's side have now lost seven of their last nine games to remain bottom of the pile.
MK Dons will move level on points with six-placed Peterborough United if they beat Darren Ferguson's side on Saturday.
Walsall also harbours play-off hopes, but could really do with a win at fifth-placed Rotherham United this weekend.
Crewe Alexandra need a victory for very different reasons when they host Oldham Athletic as Steve Davis' side battle to stay in the third tier.
Saturday's other fixtures see Bristol City host Swindon, Carlisle United take on Stevenage, Bradford entertain Gillingham and Colchester United travel to Crawley Town.
Coventry City are at home to Port Vale in the only game to be played on Sunday in League One.
