Everton are comfortable with the prospect of Manchester United returning with another bid for Leighton Baines in January to judge by Roberto Martínez's demeanour on the subject. There may be less trepidation about losing a key asset to David Moyes than there was in the summer, but it is too simplistic to say there will be no temptation should United decide to fish again.

The stance on Baines for next month is consistent with Everton's refusal to sell to the Premier League champions during their former manager's first, unproductive transfer window at Old Trafford. And rightly so. Martínez has built impressive momentum during his debut season at Goodison Park, Everton's form warrants consideration as a genuine contender for one of the Champions League places, and the club are looking to build around a core of experienced talent in January, not diminish it.

In Baines, who is in contention to return to the squad for Sunday's game against Southampton, they possess an impeccable professional, a class act on and off the pitch and a boyhood Evertonian suited to the new manager's passing style. There were no public declarations of discontent or transfer requests from the England international when his club repeatedly rejected United's offers throughout the summer. That pursuit began before Moyes had even left Everton's employment on 30 June and continued until transfer deadline day on 2 September, somewhat undermining the principled stance the Scot took on protracted courtships by wealthier clubs during his time on Merseyside.

But Everton, in truth, were not given a difficult decision to make on Baines in the summer. United made it easier for Martínez and chairman Bill Kenwright to stand their ground with underwhelming bids of £10m and £12m, the "derisory and insulting" joint £28m offer for the left-back and Marouane Fellaini – a mere £500,000 more than they ultimately paid for the hirsute midfielder alone – and were given short shrift when inquiring about a possible U-turn on deadline day.

As the Fellaini fee illustrated, Everton were always in control of transfer negotiations with United in the summer thanks to their policy – promoted by Moyes, ironically – of securing their key players to long-term contracts. Martínez reaped the benefits. As he says: "We're in a position where we can control what happens. It's different when you've got someone out of contract. The problem is when you've got no one talking about your players, because that means they're struggling. So I don't mind that as long as we are the ones who are making the calls. We are in a position now which means we can do that."

But it is not that straightforward. Baines is entering the final 18 months of his contract at Goodison and, despite encouraging noises recently about an extension, has yet to commit to a new deal that was first spoken about at the end of last season. Martínez also talked of resolving the contract issue once the summer transfer window had closed, an agreement that would force United to look elsewhere in January, but Everton head into the new year still without a resolution. But the club's target is to reward Baines, Ross Barkley and Sylvain Distin with new deals before the season is over.

Baines turned 29 on 11 December and there would be dilemmas on all sides should United finally make a serious play for the Everton defender. Would Baines find Old Trafford so alluring at present, for a start? Given his contractual position, it would make sense for the left-back to delay a decision on his future until after being involved in a World Cup in Brazil. He would know by then whether Everton or United, if any, have Champions League football to offer upon his return.

the question of Everton's finances, and whether a club that has regularly had to sell a prized asset to reinvest could afford to reject an improved offer of around £15m for a 29-year-old full-back. Everton are no longer backed into a corner financially thanks largely to the record Premier League broadcasting deal that came into effect this season. They still have money available for Martínez to spend in January from the deadline-day sales of Fellaini and Victor Anichebe. Add a fee for Baines to that pot, however, and Everton could be in a position to propose a permanent deal to Chelsea for Romelu Lukaku next summer. Just a devil's advocate thought, of course, with both clubs and the Belgium striker adamant he will be back at Stamford Bridge for the 2014-15 season.

Everton have been spared any damaging repercussions from the toe fracture Baines suffered against Liverpool on 23 November thanks to the impact of his replacement, Bryan Oviedo. The Costa Rica international has two goals and two assists in his six starts since the derby and quickly endeared himself to supporters at Goodison. Baines's statistics have dipped this season under Martínez, having created more chances for his team last season than any other player in Europe, almost a quarter of Everton's 450 opportunities during Moyes's final campaign in charge.

To suggest that Everton have a proven replacement for Baines in Oviedo would be indecently premature. It would also run counter to the optimism and adventure of Martínez's early months in charge to offload a standard-bearer like Baines while eyeing Champions League qualification. But United, if they are serious about reuniting Moyes with the left-back next month, are duty-bound to make life awkward for Everton.