Portsmouth ensured that it was to be a sorry few days for Rovers with a 1-0 win for the South Coast club.
Following on from Thursday's disappointing display against Larissa in the 2-0 UEFA Cup defeat, the home side fared better against Harry Redknapp's side but ultimately came up short in a game of few chances.
It was Nwankwo Kanu's first half strike proved to be the difference between the two sides, the former Arsenal man showing good strength to hold off Christopher Samba's attentions before rounding Brad Friedel and netting from close range.
But it could have been so different if Rovers had taken their early chances as they started brightly, looking to banish the memories of that poor performance in the UEFA Cup the previous Thursday.
Just four minutes were on the clock when the woodwork was rattled, it was a move started and ended by Roque Santa Cruz, the Paraguayan's strong forward run saw him catch the opposition on the back foot, feeding David Bentley on the flank and Santa Cruz was there at the right place and the right time to latch onto the midfielder's centre only to see his powerful header crash off the corner of post and bar and away to safety
A minute later it was Morten Gamst Pedersen's turn to test the Portsmouth defence, but his well-struck free-kick was well held by David James diving to his right.
The home side continued their bright opening when on ten minutes a centre from Bentley was half-controlled on the chest of Pedersen, the Norwegian did well to latch onto the looping ball to put it into the path of Benni McCarthy, but McCarthy, so often deadly from 12 yards, side-footed his effort just wide on the half-volley.
Two minutes later and it was Santa Cruz's turn to be provider, his strength saw him outmuscle Hreidarsson on the right wing before laying the ball inside to David Bentley, but the first-time effort from the England international flew over the crossbar.
The lack of a goal during Rovers' period of dominance proved to be costly, but not before Brad Friedel had to pull off a stunning double save to deny Kanu who had beaten the Rovers' offside trap. Firstly the American dived low to his right to push Kanu's header away, and from the rebound the Rovers number one somehow blocked Kanu's second attempt.
But that was mere respite as the visitors took the lead from their next attack on 24 minutes. A long ball thrown forward saw Kanu get the better of Christopher Samba, Friedel raced off his line, but the wily Nigerian was able to side-step the Rovers' 'keeper before keeping his cool and slotting home from a tight angle.
The home side attempted to redress the balance before the break, but despite having several promising positions, they weren't able to make more of the chances when presented to them.
Mark Hughes' side had two let-offs at the start of the second half, firstly a harmless goal-kick from David James was allowed to bounce by Samba, but he then chose to head back to Friedel, the ball going over the Rovers' number one. Thankfully the giant defender redeemed himself by clearing the ball behind as Kanu threatened to grab his second of the afternoon.
On 54 minutes Rovers again very nearly pressed the self-destruct button. Andre Ooijer's clearance out of defence was easily intercepted and Sean Davis had acres of space between him and Brad Friedel's goal. Advancing in from the right the former Fulham man had options to his left and also the opportunity of a shot, but thankfully for the home side he did neither, the resulting effort tamely rolling wide, eventually going behind off the opposite corner flag for a goal kick.
That slow start to the second period prompted Mark Hughes into making a double substitution to freshen things up, Tugay and Matt Derbyshire thrown into the mix to replace David Dunn and Benni McCarthy, but it made little difference as they continued to threaten from set-piece situations but were unable to make any of them count, a Bentley cross on 71 minutes seemed destined for the head of Christopher Samba but the returning defender couldn't apply the finishing touch.
Kanu had caused Samba and the rest of the Rovers' defence problems all afternoon, so there was perhaps some relief when he was surprisingly replaced on 69 minutes, but his replacement Benjani almost served to set up a second goal for the visitors.
Pulling out wide right to receive the ball, the Portsmouth striker held off the attentions of Andre Ooijer before delivering a dangerous low ball that found Papa Bouba Diop rushing in, but somehow from eight yards out he put his first time effort wide of goal.
With a final throw of the dice Hughes brought on Jason Roberts for Morten Gamst Pedersen, but it was Portsmouth sub Matt Taylor who very nearly made it two when he raced through onto a clever pass from Sulley Muntari before bringing to ball down and shooting low at goal only to be denied by the legs of Friedel.
David Bentley put a free-kick inches wide of David James' right post with the England goalkeeper at full stretch, but that was typical of Rovers this afternoon, they enjoyed plenty of possession, but lacked that cutting edge in the final third when it counted as a disappointing match was brought to an end by referee Chris Foy as Portsmouth enjoyed their first away win since Boxing Day 2006.
This result means a sorry few days for the Ewood Park club, but there's no time to dwell with a Carling Cup match at Ewood on Wednesday night against Birmingham City to look forward to.
ROVERS: Friedel (c), Emerton, Ooijer, Samba, Warnock, Bentley, Dunn (sub Tugay 56 mins), Savage, Pedersen (sub Roberts 79 mins), McCarthy (sub Derbyshire 56 mins), Santa Cruz.
Subs not used: Brown (GK), Mokoena.
PORTSMOUTH: James, Johnson, Hreidarsson, Diop, Muntari, Distin, Utaka (sub Pamarot 90 mins), Kranjcar (sub Taylor 86 mins), Campbell (c), Kanu (sub Benjani 69 mins), Davis.
Subs not used: Ashdown (GK), Nugent.
Booked: Diop, Muntari, James (Portsmouth)
Attendance: 19,506
