Amorebieta scores late winner for Boro
Jelle Vossen header put Boro ahead
Andre Gray levelled after Konstantopoulos error
Second leg on 15 May
Ian Holloway
Ex-Blackpool and Crystal Palace manager, BBC Radio 5 live
"What a fantastic save. He had to be every inch of his six feet five to keep that out, and I think it hit the post afterwards.
"The two teams are cancelling each other out at the moment. Both are playing 4-2-3-1. Two very good teams, though."
Brentford's Alan Judge lets fly with a superb effort from just outside the box which is arrowing towards the top corner, only for the fingertips of Dimi Konstantopoulos to push the ball onto the post. Great strike, great save - football was the winner there...
Ian Holloway
Ex-Blackpool and Crystal Palace manager, BBC Radio 5 live
"Friend's got to be careful now. That was a bit silly. Jota was going nowhere."
Jonathan Douglas plays a long free-kick over the top of the Middlesbrough defence and Andre Gray gets in between the two centre-backs and gets a touch which sends the ball goalwards from a narrow angle, forcing Dimi Konstantopoulos into a save.
Shortly after and it's another Middlesbrough yellow card as George Friend goes right through Moses Odubajo. I'm no tactical genius but you suspect Brentford will be pushing it out to the right at every opportunity now.
The first yellow card of the evening comes out with Lee Tomlin's persistent hounding of Brentford midfielder Jota eventually penalised. You suspect it won't be the first of a fiercely competitive evening...
Image source, PABBC Radio 5 live's commentary from Griffin Park has just begun - click on the Live Coverage tab to listen on desktop, tablet or mobile devices.
An excellent atmosphere and an entertaining start, but no goals as yet.
Chelsea boss Jose Mourinho is gracing Griffin Park with his presence.
Is he a) supporting his former Real Madid colleague and now Boro boss Aitor Karanka, b) checking out the form of on-loan striker Patrick Bamford, or c) a Brentford fan on the quiet?
There's definitely a touch of nerves in Brentford's play. The Bees work a promising situation out wide on the right but a constipated exchange of passes on the touchline involving Jota and Toumani Diagouraga sees the move break down.
Middlesbrough have the first corner of the match but it comes to very little. Brentford have struggled to hold on to the ball so far, which is unlike their usual possession-based approach.
A dangerous run from Boro's Lee Tomlin yields a second corner, which they play short and again any danger is snuffed out by Brentford.
Alex Pritchard, Brentford's player of the season, has a very optimistic effort with a free-kick from 35 yards out. With just one man in the wall he gets it on target but it bounces once before Dimi Konstantopoulos collects with a fair degree of ease.
Middlesbrough winger Albert Adomah makes the first attacking foray of the match, driving down the right-hand side before being dispossessed. The ball eventually makes it's way into the Brentford area but it's a comfortable take for goalkeeper David Button.
Image source, Rob Stevens/BBCBoth teams go into a pre-match huddle and then it's time.
The whistle blows and Brentford put boot to ball. We're off.
The players are out on the pitch, the banners are flying, the handshakes are under way.
Where's your money going?
The atmosphere is electric at Griffin Park, as we get ever nearer to kick-off.
The old ground - with a pub on each corner, as every football fan knows - has seldom seen a bigger day.
Image source, PABrentford have been one of the stories of English football this season, refusing to slump down the table after their impressive start to life in the Championship under Mark Warburton.
The Bees, who have relied heavily on the goals of striker Andre Gray, won their final two matches of the regular season to edge into fifth place ahead of Ipswich, Wolves and Derby.
Image source, Getty Images/BBCRob Stevens
BBC Sport at Griffin Park
Image source, PA"Former Brentford chairman Martin Lange was instrumental in the introduction of the Football League play-offs in 1986-87, but the play-offs have not been kind to the Bees.
"They have failed in each of their seven previous attempts to gain promotion through the end-of-season showpiece - including three defeats in play-off finals.
"However, this is Brentford's first shot at the play-offs in the second tier and Mark Warburton's side are looking to reach the top flight for the first time since 1947. Could this be the year their luck changes?
"Warburton is set to leave Griffin Park at the end of the season and, with question marks over the suitability of Griffin Park for Premier League football and a new stadium in the pipeline, tonight could be Brentford's last game at the ground, which has been their home since 1904."
Image source, Getty ImagesThere's live commentary of tonight's Championship play-off semi-final first leg between Brentford and Middlesbrough on BBC Radio 5 live from 20:00 BST - they will be joining the action at Griffin Park slightly late, as first they are mopping up their coverage of the general election.
Simon Brotherton and Ian Holloway, who managed Blackpool to Championship play-off final victory in 2010, are your commentary team.
It's available on desktop, tablets and mobile devices via the BBC Sport app - click on the Live Coverage tab to listen online.
Image source, Getty Images/BBCAnd let's not forget the two clean sheets kept by his understudy Tomas Mejias. Boro have the meanest defence in the second tier.
Image source, PAMiddlesbrough have been one of the most consistent teams in the Championship this season, continually occupying one of the top-six slots since early October.
On-loan Patrick Bamford - the Championship's Player of the Year - has struck 17 league goals, while their defensive unit, with keeper Dimi Konstantopoulos in fine form, keeping 21 clean sheets, which is the most in the division.