Albion cruised into the fourth round of the Emirates FA Cup after another eye-catching away performance at the Riverside.
Although former Albion loanee Chuba Akpom equalised Pascal Gross’s early opener, Adam Lallana restored the lead before the break with a simple header.
Alexis Mac Allister came off the bench to score a stylish third and also hit the post from a free kick before making it 4-1 from close range. Deniz Undav rounded off an impressive afternoon's work with a fifth goal in the closing stages.
Albion have now scored 11 goals in their last three away games and they could have had more against a Boro side who are fifth in the Championship but who were always second best here.
Roberto De Zerbi also had the luxury of giving minutes in the second half to the fit-again Adam Webster and Danny Welbeck on a satisfying afternoon for our head coach.
There were four changes to the team that beat Everton 4-1 on Tuesday with Jason Steele, Tariq Lamptey, Jan Paul van Hecke and Lallana coming in. Skipper Lewis Dunk (dead leg) missed out.
Albion made a terrific start and were ahead after eight minutes. They had already created an excellent chance when Kaoru Mitoma couldn’t quite get on the end of Solly March’s cross and March was involved again when we took the lead. Evan Ferguson’s pass found March breaking into space in the box and although Zach Steffen parried his shot, Gross latched onto the loose ball and hammered it right-footed into the net for his seventh goal of the season.
Steffen made a comfortable save after another incisive move created a shooting opportunity for Lallana. Boro had hardly threatened at this stage but they were level on 13 minutes when former Albion loanee Akpom met Ryan Giles’ left-wing cross with a powerful header which sneaked over the line despite Steele’s efforts to keep it out.
Boro fans ramped up the noise levels and Steele did well to turn Riley McGree’s left-foot strike but they were silenced again on 29 minutes when Albion regained the lead. March started the move with a cross-field ball to Mitoma. His cross from the line looped up off Tommy Smith and Lallana had an easy header virtually on the line. It was his first FA Cup goal since netting for Liverpool against Crystal Palace in February 2015.
Van Hecke was inches away from hooking home Gross’s corner and an entertaining half ended with Steele getting right behind McGree’s curling effort.
Lallana made way for Mac Allister and March had another chance three minutes into the break. Pervis Estupinan stood up an inviting cross which March met with a powerful header that Steffen parried before Boro got it clear.
Albion continued to attack with confidence and they stretched their lead in the 58th minute. Lamptey led a break from inside our half before finding Ferguson. He laid the ball back to Pervis Estupinan and his low cross was nonchalantly diverted inside the post by Mac Allister.
De Zerbi brought on Welbeck and Julio Enciso before Mac Allister went close again with a free-kick which he whipped over the wall from the left-hand corner and only just over the bar. He went even closer in the 70th minute after Caicedo was brought down 25 yards out. Mac Allister struck the ball right-footed this time and around the wall but it kissed the outside of the post with Steffen a spectator.
Akpom forced Steele into a comfortable save with 12 minutes to go but that was Boro’s first effort on target in the second half and Albion immediately went up the other end and made it 4-1 when Gross’s unselfish pull-back was swept home from six yards by Mac Allister.
Three minutes from time Albion made it 5-1. March was the creator when his pass found Undav on the right-hand side of the box and he took a couple of paces before lashing a low drive past Steffen and inside the far post.
There could have been further goals for the 700 or so Albion fans who made the 630-mile round trip but they would have been happy enough to see their side score four on the road for the second successive game and seal a place in Sunday’s fourth-round draw.
Albion will be ball number 2 in the draw, which is live on BBC 1 at 4.05pm.
Albion: Steele, Lamptey, van Hecke, Colwill, Estupinan, March, Gross, Caicedo, Mitoma (Enciso 64), Lallana (Mac Allister 45), Ferguson (Welbeck 64). Subs: McGill, Webster, Sarmiento, Undav, Gilmour.