Chelsea are “probably the underdogs” to finish in the top four this season due to a lack of singings in January, according to boss Frank Lampard.
The Blues were allowed to sign players during the January transfer window after their Fifa transfer ban was reduced on appeal in December.
But they failed to strengthen, despite links with Paris St-Germain’s Edinson Cavani and Napoli’s Dries Mertens.
“Teams have strengthened around us,” said Lampard.
“From my view, and this is not to talk ourselves down, because we’re six points clear in fourth, now we become probably the underdogs and the outsiders to some point.”
Manchester United are six points behind the Blues in the Premier League in fifth place and secured the signature of Bruno Fernandes for an initial £47m from Sporting Lisbon.
Lampard said: “If I’m looking at it with my business head on and looking around us in the table, Manchester United obviously have signed a big, world-class player in my opinion.”
The Chelsea boss also singled out Sheffield United, plus Tottenham – who signed Netherlands forward Steven Bergwijn for £27m from PSV Eindhoven – for their dealings in the transfer market.
“Sheffield United have made some fantastic signings,” added Lampard.
“Chris Wilder’s job is incredible because he’s had years to work with that group and now they are adding where they see that they need to.
“Tottenham have signed a few, and again, they are not far behind us.”
Chelsea face third-placed Leicester City at King Power Stadium in Saturday’s early kick-off at 12:30 GMT.
The Blues are without a win in their past two Premier League games, drawing 2-2 at home to Arsenal after a defeat by Newcastle at St James’ Park.
Lampard assured fans that both he and his Chelsea side are ready to finish the campaign strongly after a frustrating month of no transfer action.
“We know that recruitment is huge for a team that wants to be successful,” the Blues boss said.
“At the start of the season nobody had us in their top four, nobody.
“The reality is now that we’re in fourth but it’s going to be a real big fight.
“We have to be up for that fight, but the first person who’s up for that is me.”