Second half goals from David Norris and Luke Varney, who scored in stoppage time, rescued a point for Pompey and prevented a fourth straight opening day defeat.
Liam Lawrence was absent through injury which meant Joel Ward started on the right of midfield with Aaron Mokoena coming into the middle. Christian Dailly started on the bench, having signed a one-month contract.
After a slow start, a competitive match soon sprung to life with Pompey players making fierce challenges as tempers frayed. Dave Kitson had the first real chance of the match when Ben-Haim found him just yards out from goal but the striker could only hit the onrushing Carl Ikeme.
Boro soon had a great chance of their own when Barry Robson headed Tony McMahon's floating free kick into the arms of Jamie Ashdown.
However, Tony Mowbray's men did take the lead when Marvin Emnes, accused of diving earlier in the game by the travelling fans (it certainly wasn't a penalty), was given far too much time to turn in the box and fire the ball into the corner of the net.
The hosts took control after that and had a couple of pops at Ashdown who did well to save the one which was on target. Pompey also had a golden chance to equalise when Hayden Mullins "Quashie'd" the ball over the bar from the centre of the box.
The Middlesbrough monsoon continued with the rain coming down hard during half-time. Steve Cotterill must also have come down hard on his team as within two minutes of the restart they were level.
Mullins' pass found Norris who slammed the ball past Ikeme from outside the box but unfortunately the travelling fans' joy was short lived as Boro were soon back in front.
Pompey's defence parted like the Red Sea when Nicky Bailey found Rhys Williams in acres of space in the centre of the box and the Australian made no mistake in slotting the ball past the helpless Ashdown.
Cotterill's response was to bring on Rhys' younger brother Ryan for his Pompey debut alongside Kanu as Hermann Hreidarsson and Ricardo Rocha made way.
Playing a more open 4-4-2 system would inevitably see the home side create more chances with Pompey pressing forward and Ashdown did well to save Scott McDonald's rasping strike.
But just as if it was looking like a miserable 300 mile journey back to the south coast, Dailly's speculative long range shot deflected to the feet of Varney who struck the ball into the net in stoppage time.
That goal sent us delirious and silenced the flag-waving Boro fans to our right giving it the mouth when they should have learned from last season's match.
I'm personally delighted that we've come away from the Riverside with a point, which was probably a fair result on balance of play. What I was particularly happy with was the lack of hoof ball coming from Pompey as the players looked to play the ball on the deck.
The debutantes also made their mark with Norris probably being our best player on the day. Varney failed to beat his man on too many occasions but he is forgiven for his stoppage time strike.
Of course, not everything was perfect as a central defensive partnership that was so strong during last campaign seemed to go missing at the crucial moments, whilst Mokoena did nothing to suggest that he would be missed if he did eventually move to the middle-east.
Also, Kitson was strangely more effective out wide when he provided a couple of good crosses for other players when he should be the one on the end of them. This just proves that we are in need of another forward player at least.
Hopefully there will be more new faces to come by the time buoyant Brighton come to Fratton Park next Saturday.
Pompey Player Ratings
Jamie Ashdown: 6 - Could do nothing about the goals.
Tal Ben-Haim: 6 - Reminded us that he's actually a good footballer.
Greg Halford: 5 - Went missing for Boro's goals.
Ricardo Rocha: 5 - Was expecting better from him.
Hermann Hreidarsson: 6 - Funny watching him bomb forward at times.
Joel Ward: 6 - Still unsure where he'll play when everyone is fit.
Hayden Mullins: 7 - Got stuck in despite missing a glorious chance.
David Norris: 8 - Debut goal capped good performance.
Aaron Mokoena: 6 - Sluggish and has the turning circle of a tank.
Luke Varney: 7 - Scored vital goal.
Dave Kitson: 6 - Effective out wide but not in the centre.
Substitutes
Stephen Henderson
Christian Daily (Mullins 83): N/A - Shot led to fortunate goal.
Ryan Williams (Hreidarsson 64): N/A - Looks like he has pace.
Kanu (Rocha 64): N/A - Boro players couldn't take the ball from him.