Steve Kean reckons he pulled off the value signing of the Premier League season when he bought Yakubu Ayegbeni last summer. According to the Blackburn Rovers manager, only Newcastle United's acquisition of another African striker, the free agent Demba Ba, can compare to the snip Yakubu has proved to be since arriving at Ewood Park for £1.5m.

No wonder Kean wore the expression of a man who had dipped a hand into a supermarket's reduced-to-clear shelf and pulled out a finest range product with a 90%-off sticker after Yakubu returned from suspension to open the scoring against QPR, his 13th goal in 16 top-flight starts for Blackburn. Nine of the Nigerian's tally were scored in their five wins this term.

The comparison with the Senegalese the Senegal international Ba – 16 league goals in 19 league starts – extends beyond achievements on the pitch. Like Ba, whose own stock plummeted after Stoke City pulled out of a deal on medical grounds 13 months ago, the 29-year-old Yakubu has struggled to convince a wider audience he was worth a punt despite an exceptional career strike rate.

That career goal-ratio was diluted with only seven goals in his final 49 league appearances for Everton, who virtually gave him away four years after paying Middlesbrough £11.25m in 2007. Having rediscovered his predatory instinct on loan at Leicester City last season, however, his chance conversion rate of 39% makes him, statistically speaking, English football's No1 predator this season.

"For me, there's been the Yak and Demba Ba. If you look what those two cost in comparison to some of the other strikers, then I think they have both been bargains," said Kean. "What we like about him is when you analyse his strikes, the goalkeepers can't get set because he takes them so early. He doesn't have a lot of back-lift and before goalies know it, it's in. It's not that he does that now and again, that's his technique and if you get quality service into him there's not a better finisher."

That prowess in the penalty area led to January inquiries from some "very, very big clubs" according to Kean. "But there was absolutely no chance. I think with his goal ratio and the amount of games he's played, for him, or Ba, it would be very hard to get change out of tens of millions. That's what people who put the ball in the back of the net cost," he added.

Yakubu rarely comes alive until he sniffs an opportunity but his colleagues seemed only too willing to do his running, as he scored one and fired his only other effort off the crossbar in a first-half blitz that put the home team three up.

Jamie Mackie scored twice for QPR on his first return to the ground where he broke his right leg and was verbally abused by El-Hadji Diouf – his second goal maintaining QPR's position above Blackburn on goal difference – but Kean's body language was noticeably more relaxed. He even suggested that the renegade defender Christopher Samba, back in full training after a hamstring injury, would be back soon.

Both these clubs are now on a fortnight's break, and the former Rovers manager Mark Hughes takes his QPR squad to Portugal for four days of warm-weather training tomorrow, acutely aware of their precarious position. "It will give us the opportunity to have two sessions a day and gain a real understanding of what we've got, their personalities, and how they react to certain situations. I learnt a lot about the group here, in the performance in both halves."

Man of the match Steven Nzonzi (Blackburn Rovers)