Liam Millar's excellent goal had fired North End ahead, against the run of play in the first half, but a sustained spell of pressure saw Finn Azaz claim his first Boro goal to level it up in the second half.

Michael Carrick's team are in a slump that has brought just four wins from 13 league games and has seen them drop into the bottom half of the table, with Riis claiming goals in consecutive appearances to give Preston the three points.

The win means Preston are one of four teams level on points with sixth-placed Coventry, quite a turnaround after a slump that brought just three wins in 13 after they had made the early running in the Championship.

For Carrick, defeat brings more questions, although the lack of a regular goalscorer again cost his team after they had 20 shots to the Lilywhites' seven but could not make that advantage tell.

Preston suffered an early blow as centre back Andrew Hughes was forced off after a heavy collision with Marcus Forss, with Greg Cunningham taking his place.

Boro were on the front foot in the opening phase as Sam Greenwood was thwarted by Preston keeper Freddie Woodman after the away side pieced together a slick attack.

It was Lowe's team that broke the deadlock in the 23rd minute, however, as Matt Clarke's clearance fell to Millar on the edge of the box. His exquisite touch with his right foot took him past Jonny Howson and his left foot despatched the shot between Tom Glover and his near post.

Boro hit back as Greenwood's shot found the side netting, Azaz fired high over the bar after a corner bounced to him in space, and Forss loudly appealed for a penalty after he went down in a tangle with Cunningham.

The visitors continued to push after the break, with Azaz seeing one shot deflect just wide, but his big moment arrived in the 58th minute.

The man who signed from Aston Villa in the January window got off the mark for his new club in fine style, feinting one way to lose the attentions of Alan Browne and then curling a lovely shot into the top corner to level the scores.

Boro deserved equity, but nobody deserved what came next, just three minutes later.

Will Keane's shot was going nowhere but it took a big deflection off Rav van den Berg that looped beyond the stranded Glover and left Riis with an open goal.

Again Boro went forward but Preston defended with grit as Liam Lindsay bravely stuck his head in the way of a fierce Howson shot that looked destined for the corner of the net, Woodman pulled off a great save from Forss' volley and then kept out Sam Silvera after the substitute had wormed his way past two defenders.

At the other end Milutin Osmajic had a great chance to seal the victory late in the game but found Glover was alert to smother his shot.

Preston manager Ryan Lowe told BBC Radio Lancashire:

"I told the players that sometimes you can't help but drop the way we dropped, and soak it up. We gave the ball away more than a couple of times to let them have penetration on us.

"The first-half performance was OK and we went in 1-0, but they came out in the second half and gave it a right good go. For their goal, you can't give a player of that calibre that much time, but for us to show the resilience and character to get right back into the game right afterwards was massively pleasing.

"That's three on the bounce, all fantastic team performances in different ways.

"We were tactically astute and kept them at bay, and so were well worth the three points."

Middlesbrough manager Michael Carrick told BBC Radio Tees:

"It's a tough result to take, the results definitely aren't going our way. We definitely deserved more out of the game, but we're not getting it and we have to do something about it.

"I can't fault the boys' effort and some of the quality of the play was really, really good but we don't have the balance between performance and result at the moment. They hadn't had a touch in our box and suddenly we were 1-0 down, which has happened two or three times over the last six weeks or so.

"We had enough to win the game but moments are killing us. Of course we have to defend better at times, to block shots and stop shots and score at the other end.

"Finn [Azaz] showed his quality and you can see him settling into it. It's a big goal for him."