Brendan Rodgers admitted that Celtic face a genuine challenge to retain their Premiership crown.
His team were comfortable champions during Rodgers' first two seasons in charge, but the title holders went into the winter break leading Rangers on goal difference only, albeit with a game in hand.
With Kilmarnock a solitary point further back and Aberdeen three off the pace, the Parkhead boss admits there has been an all-round improvement in standards that poses a threat to Celtic's quest for an eighth successive crown.
Rodgers admits Rangers' recruitment drive under his former Liverpool captain Steven Gerrard presents a particular threat - but he has backed his players to rise to the test.
He said: 'There's no doubt there's a challenge now. I try not to overthink that and focus on ourselves. I concentrate on improving our standard - that's what it will be about, ultimately.
'That was the same in my first year here when the gap was 20 points.
'Rangers have invested well. They've brought in good players. Steven has done really well bringing them together.
'Other teams are also up there and the standard of the league has improved, which is great for Scottish football.' Defeat to Rangers in the post-Christmas fixture at Ibrox consigned Rodgers to his first derby loss in 13 matches and Gerrard has taken that momentum into his January transfer dealings, quickly adding the experience of Steven Davis and Jermain Defoe.
Rodgers, too, has been busy, acquiring Oliver Burke and Timothy Weah on loan, while striker Vakoun Issouf Bayo has been purchased for £2million - and American left-back Andrew Guzman is awaiting a work permit.
The manager believes the real key to success will be ensuring his squad adhere to the principles that have yielded a clean sweep of available domestic silverware on his watch.
He continued: 'When you lose a game to Rangers, things are said.
'But you must stay calm and focused on the field. The method is key for us, the way we work, and the continuation of that.
'We've been consistent over the last couple of years and we don't need to change that. For us, the challenge feels good.
'It's what these players always respond to.' Rodgers remains in the hunt for a right-back as a successor to Mikael Lustig, who is out of contract at the end of the season.
With Atalanta seeking £10m for Belgian internationalist Timothy Castagne, Celtic have switched attention to Omar Elabdellaoui of Olympiakos.
AIK Stockholm are monitoring Lustig's situation, with a view to taking the player back to his homeland.