Frank Lampard believes Chelsea's failure to bring in new signings in the January transfer window has left them as "underdogs" in the battle for Champions League qualification.

Chelsea had their two-window transfer ban halved, meaning they could add to the squad for the second half of the season, but the club failed to make the most of their opportunity.

Lampard wore a frustrated expression as he faced the media on Friday, confirming neither Dries Mertens nor Edinson Cavani - two mooted targets - would be signing.

Wantaway forward Olivier Giroud therefore stayed at Stamford Bridge, and Lampard pointed to the business at rival clubs to show where Chelsea, fourth in the Premier League, may slip behind.

Manchester United brought in Bruno Fernandes and Odion Ighalo, while Tottenham signed Gedson Fernandes and Steven Bergwijn.

Lampard even referenced the business done by eighth-placed Sheffield United, who spent a club-record fee on Sander Berge.

"I look at Manchester United signing a big, big player, a world-class player [Fernandes] in my opinion," Lampard said.

"And the teams around us, Sheffield United making fantastic signings. Chris Wilder's job is incredible because he's had years to work that group and now they're adding where he sees fit.

"Tottenham have signed a few and they're not far behind us. And not only have they signed a few but a couple of players have left where the situation was they were towards the end of their contracts and maybe weren't happy being at the club any more. Sometimes that's as important as bringing players in.

"Now what remains to be seen will be seen and 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 because the teams around us have strengthened. It's a fact."

Lampard said the previous ban had made January "a bit more crucial" for Chelsea but vowed he would not continue to bemoan their lack of movement.

"I have to be the first person who remains positive and I have to be truthful when I speak out loud," he said.

"We know that recruitment is huge for a team that wants to be successful. Look no further than Liverpool and Manchester City in recent years.

"But it's a fact. People will get bored if I keep crying about that fact. I have to work. The players have to work.

"I think, at the start of the season, nobody had us in their top four. The reality is that now we're in fourth but it's going to be a real big fight.

"Let's not forget it's a difficult window. The fact we missed the last window made it a bit more crucial for us."