Thierry Henry said he will not be convinced that Chelsea is ready to challenge for the title until the team beats one of its direct competitors.
Enzo Maresca's men currently find themselves in second place in the Premier League, two points behind Liverpool having played one game more than than the Reds.
The Stamford Bridge club is on a five-game winning streak in the league, but picked up just one point from games against Manchester City, Liverpool and Arsenal in the first half of the campaign. City recorded a 2-0 win in West London on the season's opening weekend, before Chelsea suffered a 2-1 defeat at Anfield in October and drew 1-1 with Arsenal a month later.
Chelsea boss Maresca has been keen to play down title talk surrounding his young side, and Henry thinks the team needs to take a big scalp to really put a marker down.
"We've seen teams before that nobody expected to do it, reaching it," Henry said on Sky Sports. "But I'm just thinking one thing they still didn't do is to beat a team that's in and around them.
"They still didn't beat a big team. They came back against Tottenham (to win 4-3), but show me you can beat Liverpool, show me you can beat City, show me you can beat Arsenal, and then you will be like, 'oh, hang on a minute, wait'. You see what I mean? There is a step there."
Jamie Carragher, meanwhile, thinks Chelsea's trip to Everton this weekend could show a lot about the character of the team.
"I think Chelsea against Everton next weekend is really important," Carragher said. "You might say, Chelsea are near the top of the league and Everton are near the bottom, but when I look at the things that worry me about Chelsea in terms of winning the league: a goalkeeper, maybe two center-backs — Goodison Park is the kind of place where something like that would show up.
"If they can go to Goodison, keep a clean sheet and win, you think, 'oh. ok'. That's one of those results where it's a team near the bottom but you know it's a tough place to go. If your goalkeeper's not at it or your two center-backs are not at it... set pieces, Everton's tight pitch... you can come a cropper there."