Toure, a midfield talisman at the Etihad Stadium since his signing from Barcelona in 2010, has performed below his usual high standards for much of the current season.
He was sent off for an act of petulance in the midweek Champions League loss to CSKA Moscow and there have been reports that City are now willing to consider offloading him.
Paris St Germain have been linked with the Ivory Coast international but Pellegrini is adamant the 31-year-old will be staying.
Pellegrini said: "There must be a lot of reports telling (the story) that Yaya will be sold
Maybe (it is) all the other teams that want Manchester City to be a weaker team.
"Yaya is a very important player
He played very well in the first half (against CSKA) - he scored a goal
In the second half he made a mistake and he was sent off but - never in my mind - I am sure nobody at the club is talking about selling Yaya Toure.
"Maybe that news comes from other teams (who want) to see our team weaker."
Toure was outstanding as City won the Barclays Premier League last season, scoring 20 goals in the competition.
Problems began in the summer, however, as he voiced criticisms of the club and then became embroiled in a row over how his birthday was celebrated.
There was also tragedy as his brother Ibrahim lost his battle with cancer and earlier this week he was the victim of racial abuse after reactivating his Twitter account.
His form on the pitch is part-reflected in City's underwhelming start to the season
City are yet to hit their stride in the Premier League and are facing early elimination from the Champions League.
Last Sunday's derby victory over Manchester United was City's only win in five games.
As well as players' performances being questioned, Pellegrini is also starting to find himself in the firing line, but the former Real Madrid coach has again insisted he does not feel pressure.
The Chilean said: "I never feel pressure
In my career I have had 25 years managing teams and the only pressure I feel is my own pressure to return to play in the way I like this team to play, to play attractive football and be a winning team.
"I don't read press, I don't have any other pressures
I don't feel external pressure (and have not done) in my whole career."
Pellegrini insists it is too early to be writing off his side
They trail leaders Chelsea by six points in the Premier League but are still third
At the equivalent stage last season City were fifth, trailing then leaders Arsenal by six points.
The Champions League challenge is more precarious, with just two points gained from four group games but City could yet progress if they can hit form against Bayern Munich and Roma.
Pellegrini said: "It is difficult to progress in the Premier League when you won the title last year but we try to continue fighting for the title.
"I don't know if you can take some conclusions when you have to play 28 games more
It is a lot of games and we are just in November.
"About the Champions League, we have to take the conclusions when we have finished the group
If we don't qualify it will be a step back but you can't talk about things you don't know will happen.
"I always say that mathematics can give you qualification and we are going to fight for it
We have six more points to play for."
Pellegrini is hoping for a reaction as City travel to QPR, although weakened by the absence of injured captain Vincent Kompany, on Saturday.
He said: "Yes of course, I want to see the same team we saw in the derby three days before.
"It is very important to return to the Premier League, trying to continue winning so we can fight for the title until the end.
"In this moment we turn the page because it is very important to continue in Premier League the way we are doing now
We have won four of five games that we played in the Premier League.
"It is difficult to recover physically and mentally in less than 72 hours from what happened on Wednesday but we are trying to do it and I hope tomorrow the team that start will have the answer for the moment."
Six years ago Charlie Austin was a part-time bricklayer and playing for Poole Town but QPR boss Harry Redknapp believes the now-Premier League striker can cap his incredible rise by cementing his place in the England squad.
Austin helped Poole win the 2009 Wessex Premier Division - the ninth tier of English football - with 46 goals in all competitions while also holding down a day-job on a Bournemouth building site.
Transfers to Swindon and Burnley followed before Austin's sharp-shooting persuaded QPR to make their move in August 2013
He already has five goals in the top flight this season.
The 25-year-old was not included in Roy Hodgson's latest England squad on Thursday but if Austin can maintain his current form, Redknapp believes an international call-up will not be far away.
"Charlie's improving and if he keeps scoring goals there's no reason why he can't play for England in the future," Redknapp said.
"He's a great lad, he's got a good attitude, he comes in every day wanting to work and with a smile on his face and wanting to be a footballer.
"He's had it hard, he used to get up early in the morning to do bricklaying in the middle of winter and I think he realises how fortunate he is.
"He loves it and he deserves it - if he keeps scoring goals and keeps improving his game there's no reason why he couldn't make the breakthrough (to the England squad)."
Redknapp said Hodgson is yet to enquire about Austin's services but his instinctive flick-finish against Chelsea last weekend will likely not have gone unnoticed by the England boss.
Hodgson may also be attracted to the striker's drive and enthusiasm - traits that have not always been apparent in Rangers' displays this season.
"It's great to see lads who appreciate what they're getting," Redknapp said.
"They're coming out and playing football for a couple of hours every day and getting well paid.
"He probably remembers getting up at half five in the morning laying bricks through the winter on a building site - this is fantastic for him.
"Maybe we should send a few more out on building sites on work experience - it wouldn't do them any harm.
"I sent kids out on loan at West Ham
Frank Lampard was sent out to Swansea in the old fourth division where they had to wash their own kit after training.
"It toughened them up and made them realise how lucky they were."
Austin's remarkable rise from the lower leagues is particularly pertinent given Rangers host big-spending Manchester City on Saturday.
In 2009, while Austin was playing the likes of Alresford Town and Bemerton Heath Harlequins, his opposite number Sergio Aguero was already scoring goals in the Champions League for Atletico Madrid.
Aguero, who joined City for £38million in July 2011, has scored six times in his last four games and Redknapp believes Rangers must find a way to stop the Argentine to have any success on on Saturday.
"Aguero is worth £38m in my opinion - he looks cheap at that money, he's a fantastic player," Redknapp said.
"I certainly don't underestimate City in any way shape or form.
"Aguero is just an amazing player, Yaya Toure is world class - they are full of top quality players.
"We'll have to be at our best but if we are then we have a good chance."
QPR's Joey Barton and Nedum Onuoha could both return to face their former club.
Barton and Onuoha are available again to Harry Redknapp as is midfielder Jordon Mutch
All three missed last weekend's 2-1 defeat at Chelsea with hamstring problems.
Rio Ferdinand is serving a three-match ban for comments made on Twitter while Alejandro Faurlin is a long-term absentee with a cruciate ligament injury.
Source : PA
Source: PA