Scottish Premiership players return from international duty in all corners of the world in time for five top-flight fixtures on Saturday and one on Sunday.

Reigning champions Celtic and rejuvenated Aberdeen, separated by goal difference at the top with 100% records, could be further ahead by the time the sides in third and fourth, Dundee United and Rangers, meet on Sunday.

Here are some of the key things to look out for this weekend.

Considering Jim Goodwin's United are newly promoted and lost their latest four meetings with Rangers when they were last in the Premiership, you would expect last season's runners-up to be strong favourites despite the game being at Tannadice.

But this is a different United - and a different Rangers.

This is the first opportunity Philippe Clement's visitors have had to redeem themselves after their shortcomings were exposed again by champions Celtic.

A crushing 3-0 defeat in the first Old Firm derby of the season not only leaves Rangers five points behind their city rivals and Aberdeen after only four games but also down in fourth place - one point behind Sunday's hosts.

They head to Tannadice without a win in their three away games this season - and have only won one of their last seven on the road in the Premiership stretching into last term.

Clement insisted in this week's question and answer session with supporters that he believes his side can still win the title - and fans currently appear more inclined to blame the Ibrox club's board for squad weaknesses.

However, with the leading two playing a day earlier, Rangers could find themselves eight points adrift by kick-off in Tayside and pressure will only mount on the Belgian if they end the weekend further behind.

It is certainly not the ideal time to be visiting a side who are unbeaten in eight outings, winning their latest three, and who have not lost in 10 home games - five of them this season.

One thing both sides have in common is an eye for taking their chances.

Rangers' expected goals from non-penalty shots in the Premiership this season is the highest of any side at 0.148, with United in third with an average of 0.124, and such clinical finishing could make the difference.

It is little wonder that reports this week suggest signing Jamie McGrath beyond the end of the midfielder's current contract next summer is one of Jimmy Thelin's priorities now that the transfer window has closed.

The new manager's signing of Norwegian veteran Sivert Heltne Nilsen from Brann to occupy a holding role in midfield has allowed McGrath and Graeme Shinnie to focus on the more creative, attacking sides of their skillset.

Indeed, Republic of Ireland 27-year-old McGrath has responded by creating more chances (17) and more assists (three) than any other player in the Premiership so far, as well scoring three goals in all competitions.

Assuming he recovers from the head knock that forced him off early in the 1-0 win away to Ross County last time out, he will be pivotal in Aberdeen's attempt to stretch their winning run this season to 10 games.

Five of those have come at home, with an aggregate score of 14-2, and the home winning sequence is now at eight running into last season - 12 unbeaten.

McGrath and his mates will be favourites to stretch their unbeaten run against Motherwell to seven games, but Thelin will be keen for his key midfielder to be passed fit considering Stuart Kettlewell's visitors are themselves on a three-game winning streak.

What a difference a few weeks make in football.

Hearts had gone into the new season having strolled to a third-place finish and with the promise of consolidation as Steven Naismith made his moves to strengthen the squad early in the summer transfer market.

In contrast, champions Celtic spent much of the summer being berated by their fans for their lack of activity while waiting for the almost inevitable departure of star midfielder Matt O'Riley.

However, a late flurry of activity on the back of a record sale to Brighton & Hove Albion and Hearts on Saturday face the prospect of facing a side seeking their sixth consecutive win since the start of the season while poised to hand a first start to their own record signing.

As Arne Engels quickly followed his arrival from Augsburg by celebrating his 21st birthday with a first cap for Belgium, Naismith was having to admit that his own summer arrivals needed more time to adapt to the pressure of playing for a bigger club than those for whom they had played previously.

The Tynecastle head coach is facing the heat after suffering six defeats in a row - just one point from their opening four league games being Hearts' poorest start to a top-flight campaign in the 21st century.

Talisman Lawrence Shankland embodies the general malaise, the Scotland striker having failed to score this season despite having the most shots of any player in the Premiership.

Hardly the ideal time to be visiting a side who have only conceded once this season - in a 3-1 League Cup win over Hibernian - and who are one game away from matching the feat of five opening league games without losing a goal achieved only once before - under Willie Maley in 1906-07.

Naismith proved he could conjure upsets against Brendan Rodgers' side with two wins out of four meetings last season, including a 2-0 win at Celtic Park in December.

Meanwhile, Shankland's six goals against Celtic in the league since the start of the 2022-23 are as many as he has against any other opponent.

What manager and captain would give for a repeat on Saturday.