Blackpool's goalscorer Jamille Matt is replaced by Armand Gnanduillet.
Semedo goes narrowly close with his effort to claim the home side's first shot of the second half.
Blackpool make their first substitute as Jim McAllister replaces Colin Daniel.
An Orient breakaway sees Semedo blaze his shot high and wide.
A free-kick on the corner of the box for Orient results to nothing as Blackpool look like taking away all three points.
Orient make their final change as Paul McCallum comes on for Ollie Palmer.
Vassell unleashes a stinging 25 yard effort that scrapes the top of the crossbar, as Blackpool are the most likely team to grab the next goal.
The Tangerines almost make it three but Kelvin Mellor's drilled effort goes just over the bar.
Seems strange considering Orient are 2-0 down, with two strikers on the bench but Cavasin decides against bringing neither of them on.
Second change for Orient as Collins is replaced by Sandro Semedo.
On many occasions this season, the O's have run out of ideas when they've gone behind and the same has happened today as the home side have hardly threatened in the second half, with Blackpool cruising so far.
From the resulting corner, Tom Aldred, who was booked for handball moments ago, looked like he put the ball in the net with his hand. However, referee Brendan Malone thought otherwise and the visitors are now 2-0 up.
Kyle Vassell takes on Parkes, who is easily beaten, but Vassell's effort is well saved by Cisak to keep Orient alive.
Attendance for today is 4,376, with 361 Blackpool fans.
Orient make their first change as Erichot is replaced by Alan Dunne.
Yellow card for Tom Aldred for handball just outside the area. Free-kick to Orient in Callum Kennedy territory.
Blackpool captain Danny Pugh pretending to lie unconscious after being hit in the face with the ball from Atangana's attempted cross really has ruffled the feathers of the Orient fans.
Michael Collins get the game back underway for Orient.
Both teams now out ready for the second half.
Despite good attacking prowess at the end of the first 45 minutes, Orient are behind again, but, there are good signs of encouragement.
Half-time: Leyton Orient 0-1 Blackpool
Fourth Official Michael George has brandished a minimum of two minutes added time to the first half.
Daniel look to have broken free from the Orient backline in a one on one goal scoring opportunity but Cisak did well to deny the versatile Blackpool man.
Centre half Tom Parkes expressed his 'inner Lionel Messi' with a neat flick towards goal before smashing a volley just over the cross bar.
Collins causing problems for the Blackpool back line as the ex-Hartlepool player's shot in the box is well blocked.
Nicky Hunt's left footed cross was pounced on by Michael Collins, who rounded the keeper and finished well, but the fourth official judged Collins in an offside position.
GOAL DISSALLOWED FOR ORIENT
Left back Andy Taylor's effort from the free-kick is well parried by Cisak
Blackpool have a free kick in a dangerous position
It would of been one the goals of the season, for sure!
SO CLOSE FROM ORIENT!! Massey produces a 25 yard pile driver that was a lick of paint away from rattling the net, as his effort rattles the crossbar.
Attacker Jamille Matt easily outmuscles Erichot to win the ball on the left hand side, before entering the area and producing a fine finish past Cisak and into the roof of the net.
A lucky escape for the hosts.
A poor Erichot clearance fell to Colin Daniel, but the latter blazed over from the edge of the area.
Orient battling hard in a couple of meaty challenges that involved Massey and Hunt. Really great to see
The home supporters seem to pretty pleased with how their players are performing and are making lots of noise.
Apologies, brief loss of internet connection, but lucky for you, nothing was missed as the score remains goalless.
A fantastic Orient counter attack led by Massey and Simpson has lifted the mood here at The Matchroom Stadium, but it resulted in Massey's effort being well saved and was judged offside.
Cisak process a solid stop from Brad Potts in the area as the latter tried to lift the ball over the shot stopper from eight yards out.
Fans favourite Nigel Atangana has Orient's firs shot on target, but the former Portsmouth man's tame effort is easily dealt with by Sam Slocombe.
The O's have stuck with the same formation as last week, going with the 4-4-2 diamond formation, with Weir protecting the backline, Atangana on the right, Massey on the left and Collins giving support to Simpson and Palmer up front.
The visitors have started much the better team, dominating possession and have pressurised Orient on several occasions.