Chelsea boss Frank Lampard has reiterated he is in the market for a new striker as he is still unsure about the full extent of Tammy Abraham's ankle injury.

Abraham collided with the pitchside advertising hoardings in the closing stages of Chelsea's 2-2 draw with Arsenal on Tuesday and was later seen limping away from Stamford Bridge.

The England international did not fracture a bone in the incident, but it remains unclear how long he will spend on the sidelines and Lampard is actively seeking back-up.

"The good news is he hasn't fractured anything - we were worried about a hairline fracture," Lampard said at Friday's pre-match news conference ahead of the FA Cup fourth-round tie with Hull City.

"The other news is we still have to see how he develops. It's not a clear-cut one. He's not fit for the weekend, but whether he'll be fit for [the Premier League game against] Leicester [on February 1] I'm still not sure. 

"I haven't got great news, or the news for you. It's still not clear at the moment."

Chelsea have scored seven times in their last four matches but Lampard has challenged his players to be more ruthless in front of goal.

"I think the impetus to bring in a striker or players potentially that can get on the end of these chances we're creating is there, and we have to be really honest about that," he said.

"Recent games have shown that if we are struggling to create that's one problem, but when you're creating 20 chances a game and not scoring enough goals that can be crucial.

"So I don't think it absolutely changes it but Tammy of course has been our main source of goals, so yes, it's very relevant."

Lampard last week hinted at his interest in Edinson Cavani as a possible short-term fix, but Atletico Madrid are the favourites to sign the Paris Saint-Germain star.

And the former Derby County coach acknowledged trying to strengthen a squad in the mid-season window is far from easy.

"I think there's choice, but it's not the ideal window, " he said. "I think history has proven that, albeit there have been some good signings in January for clubs that have made a difference both long-term and short-term.

"I think it's about trying to get the choice right of the player that we can bring in considering what is available. 

"The club know, I'm saying pretty much the same thing every press conference, and the games are showing that, the club know my thoughts on that. So we'll have to see at the time the window shuts."

Despite a lack of striking options, Lampard also suggested Olivier Giroud - a rumoured target for Barcelona and Inter - could be on his way out before the window closes.

"With Olivier it's still the same position where there's been contact with other clubs and if and when that's agreed I'll let you know, but it's not yet," Lampard said. "He's still our player on those terms."