Jermain Defoe’s move to Rangers was described as a "massive statement" and a potential "game-changer", but how has he settled at Ibrox? And what has his arrival meant for Alfredos Morelos? We take a look ahead of Rangers’ trip to Aberdeen, live on Sky Sports.

After a difficult first half of the season with Bournemouth, it hasn’t taken Defoe long to get back among the goals at Rangers. He arrived early in the month and, unlike if he had signed for a Premier League or EFL team, he had the benefit of joining a winter training camp in Tenerife to help ease him into things.

His made his debut against Kilmarnock on January 23, with manager Steven Gerrard changing formation to accommodate his former England team-mate.

Whereas before the winter break he had largely deployed Alfredo Morelos up front on his own, now he switched to 4-4-2 with a diamond shape in midfield.

Defoe, who only played 21 Premier League minutes in the first half of the season with Bournemouth, scored early, but the tactical switch did not pay off as Rangers lost 2-1.

Rangers have played three times since that match, winning all three matches, with three different forward lines.

Morelos led the line in a 3-0 win over Livingston; Defoe and Kyle Lafferty started in a 3-1 Scottish Cup win over Cowdenbeath; and Defoe and Morelos started together in Saturday’s 4-0 win over St Mirren.

Former Scotland international James McFadden thinks Rangers look better with more width.

I think their best performances have been in a 4-3-3, he told Sky Sports. Look at the Old Firm game before the winter break, their wide players were excellent, the pressure was brilliant and allowed them a good base to press.

Even the performance at Livingston, there was high pressure and intensity and the wide players were the standout performers. I feel that’s where Gerrard is getting the best from his side, by using his wide players.

Ryan Kent has been in excellent form and Daniel Candeias has done well. Morelos at the minute seems to be better on his own up front.

Morelos is Rangers’ leading scorer this season with 13 goals in the Scottish Premiership. While there was speculation over his future last month, Gerrard was firm in his desire to keep the striker, who team-mate Andy Halliday has called the best player in the country this season.

Morelos’ importance to Rangers means the arrival of Defoe has seen others miss out. Kent and Candeias have both dropped to the bench as Gerrard has shuffled his side and tried to find roles for Defoe and fellow January signing Steven Davis.

The debate over the team selection is likely to cool if Defoe and Morelos strike up a strong partnership, but McFadden warns this will take time.

Morelos is used to playing on his own. In order to get the best from a partnership it needs time to grow. That’s something Steven Gerrard will be looking at, but it won’t happen overnight. They are good players and will get an understanding but it takes time.

Morelos, when he’s on the pitch, is a huge asset, he occupies defences, works hard, brings team-mates into play and scores goals.

Defoe, who is a forward that usually likes to play off the last man, has been part of a number of partnerships during his career. Morelos, meanwhile, has looked at his best playing as a lone striker at Rangers.

After playing Morelos and Defoe together in Rangers’ 2-1 defeat to Kilmarnock, Gerrard said the result was nothing to do with tactics or formation. However, in the next game Gerrard reverted to a 4-3-3 with Morelos up front and Candeias and Kent, who have been key players for Rangers this season, both in the side.

The changes produced a much-improved display.

So what can Gerrard do?

When Defoe was signed, Gerrard said that if we use him with another forward, everyone else will maybe have to adapt and evolve.

But in such a close title race, time is not on Gerrard’s side. If Rangers are to catch Celtic then they cannot afford slip-ups and do not have many opportunities to experiment, as the defeat at Kilmarnock showed.

There have also been questions about whether the Rangers manager feels pressure to get Defoe, along with Davis, into the starting XI after they were signed on loan. Omitting either Candeias or Kent then has the potential to leave him open to criticism if their replacements do not impress.

Rangers started with a diamond in their 4-0 win over St Mirren on Saturday, but, as Gerrard acknowledged, they improved with the introduction of Candeias after half-time.

There was an improvement in the second half, we passed it better and created more. We looked better when we went to 4-4-2 with the wingers.

Defoe, who scored a penalty in the win over St Mirren, has been full of praise for Morelos, saying he is so sharp, he is aggressive…and relentless with his running.

But Gerrard faces a decision ahead of a crucial trip to Aberdeen, who would move into second above Rangers if they win on Wednesday. The Dons have won two and drawn one of their three meetings with Rangers this season and Morelos was sent off in both the league matches.

Will Gerrard stick with Morelos? Or will he add Defoe into the mix? How he manages and moulds the duo could be decisive in determining the success of Rangers’ season.

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(c) Sky News 2019: Steven Gerrard facing decisions over Jermain Defoe and Alfredo Morelos partnership at Rangers