Orient dropped their first points of the season as they drew 1-1 at home to 10-man Walsall on Saturday afternoon, but the result means they remain unbeaten in the league with a three-point advantage at the top of the table.
The visitors saw captain Andy Butler given his marching orders on 17 minutes for a poor challenge on Romain Vincelot and the O's took advantage of the extra man to dominate the first half, opening the scoring seven minutes before the break thanks to David Mooney's ninth goal of the season.
However Orient failed to maintain their momentum and intensity in the second period and allowed Walsall to equalise through their top-scorer, Craig Westcarr, on 71 minutes.
And a frustrating afternoon for the O's was compounded in the final minute of second-half stoppage time when Vincelot was handed his second yellow card of the game for a late tackle on the visitors' goalscorer.
Orient boss Russell Slade had explained in the build up this game that he feared he may have to make at least one change to the starting XI that was victorious away to Brentford on Monday evening due to a couple of injury concerns.
However O's defenders Mathieu Baudry and Scott Cuthbert were deemed fit enough to start the game meaning Slade could name the same lineup he has done for the past eight league games.
Walsall made two changes to the team that drew 1-1 with Rotherham last weekend; manager Dean Smith recalling Westcarr and Milan Lalkovic to the starting XI.
Both sides were high on confidence going into this meeting, with Orient enjoying a well-documented 100% start to the season which had seen them race into an early five-point lead at the top of League 1 while Walsall were unbeaten in three games which had lifted them to seventh place, just a point off the play-offs.
The visitors lined up with a five-man midfield and this was certainly a contributing factor to the lack of goalmouth action early on in the game, with neither side managing to forge out a clear opening.
The closest both came to finding the net was with a headed effort each. First, Walsall skipper Butler sent his effort flying just wide of Jamie Jones's right-hand post, then Dean Cox - probably the smallest man on the pitch - snuck in behind the opposition defence to get on the end of a Moses Odubajo cross, only to see his low header deflected wide for a corner.
The afternoon's first significant event occurred on 17 minutes when Butler became the third player to be sent off against Orient this season. The defender flew into a challenge on Vincelot on the O's right wing and referee Graham Scott wasted no time in pulling out the red card, giving the West-Midlanders a mountain to climb against the league leaders.
As the half progressed, Orient's extra man began to show, particularly when working the ball wide to the likes of Moses Odubajo who sent in a handful of teasing crosses that were well defended by the visitors.
It was the O's right wing that was the continuing source for most of the O's chances, and it was from here that Lloyd James sent in a cross that led to the opening goal.
Lisbie went up to challenge Walsall goalkeeper Richard O'Donnell for the ball and, after it seemed like the keeper had comfortably won the aerial battle, he fumbled the cross straight into the path of Mooney who fired a first-time half-volley low into the net on 38 minutes.
Shortly after conceding, O'Donnell managed to get the better of the O's attack when he came off his line well to block a shot from Lisbie. The save seemed to reinvigorate his team and the visitors enjoyed their best spell of the game in the lead up to half-time, during which they won a series of corners.
However, the O's defence picked up from where they left off against Brentford earlier in the week and looked in no danger of letting Walsall get themselves back in the game before the break, with goalscorer Mooney chipping in with a couple of textbook defensive headers to clear the danger.
It was an end-to-end start to the second half on a grey afternoon in E10.
However it took until 53 minutes before either keeper was forced into a save when Cox - continuing to roam infield from the left wing - found himself one-on-one with O'Donnell who narrowed the angle well and managed to get his outstretched leg to the winger's low shot.
The hour-mark came and went without any sign of another goal for either side and Orient were beginning to show signs that their concentration was dropping. The intensity was not at the level it was in the first-half and a number of uncharacteristically stray passes from the likes of James and Vincelot were beginning to give the visitors hope that a comeback was possible.
And on 71 minutes, the home side were punished for taking their foot off the gas. A deep cross from Walsall's left was headed back across goal by striker Tony Hewitt into the path of Westcarr who beat the O's defence to the ball to nod home from close range.
The equaliser did inject a bit of urgency into the O's play and they might have regained the lead just a couple of minutes later if it wasn't for a brilliant one-handed save from O'Donnell which kept out Lisbie's powerful header after a pinpoint delivery from Vincelot.
Slade sent on Shaun Batt, who scored his second league goal of the season against Brentford on Monday night, in place of defender Cuthbert with 15 minutes remaining - showing the manager's intent to take all three points from a game in which they had an extra man for such a lengthy period.
The O's began to camp inside the opposition's half as the game wore on but Walsall were remaining resilient at the back, giving the home side little space to get in behind.
However substitute Batt managed to turn his man and get a dangerous cross away on 89 minutes, leading to a corner for the hosts. Baudry got his heavily bandaged head to the resulting corner kick only for O'Donnell to tip it on to the bar - a stunning save which ensured he was fully redeemed for his poor handling which led to the O's first half goal.
The home crowd - which, at 5,429, was a season's high - were spurred on when the fourth official's board signalled there would be five minutes of additional time but the O's could not galvanise themselves enough to find the winner.
The game finished on a sour note when Vincelot was shown a second yellow card for his strong challenge on Westcarr in the dying moments of stoppage time, and there was even time for Batt and Walsall midfielder Adam Chambers to pick up a booking each before the referee brought proceedings to a close.
Orient will be disappointed they did not capitalise on their one-man advantage and strong first-half performance but the point ensures they will go into next week's game at Oldham top of the league by three points.
ORIENT: Jones, Omozusi, Clarke (C), Baudry, Cuthbert (Batt, 75), Cox, James, Vincelot, Odubajo, Mooney, Lisbie (Stockley, 85).
SUBS: Larkins, Sawyer, Lasimant, Gorman, Bartley
GOALS: Mooney (38)
BOOKINGS: Batt (90+7)
REDS: Vincelot (90+6 2 yellows)
WALSALL: O'Donnell, Taylor, Butler (C), Featherstone (Purkiss, 22), J.Chambers (Benning, 88), Mantom, Lalkovic (Baxendale, 68), Westcarr, Downing, A.Chambers, Hewitt
SUBS: Hemmings, Roberts, Sawyers, McQuilken
GOALS: (Westcarr, 71)
BOOKINGS: Chambers (90+7)
REDS: Butler (17)
REFEREE: Graham Scott
ATTENDANCE: 5,429 (355)