One of many contributing factors in Carlisle United's upturn under Paul Simpson has been the stability when it comes to team selection.

With the exception of the midweek visit of Newport County, the Blues have largely kept faith with the same clutch of players.

But Simpson could be forced into one major change for the clash with Bristol Rovers on Saturday, given captain Callum Guy is likely to miss out through the injury he sustained during the win at Barrow.

READ MORE: This is what Paul Simpson has said about Callum Guy's injury

Guy is not an easy figure to replace in the side given his significance to the side - particularly in the 5-3-2 system currently being utilised by the Cumbrians.

His discipline in the centre of the park allows the other two members of Carlisle's midfield trio to push further forward, while his set-piece ability is also something the side will have to try and replace.

So Simpson will no doubt be weighing-up a number of options to try and fill the void left by his skipper.

Here, we take a look at four of the potential replacements for Guy:

Corey Whelan

News and Star: Corey Whelan replaced Callum Guy at BarrowCorey Whelan replaced Callum Guy at Barrow

Whelan was the option chosen by Simpson to replace Guy at Barrow, with the former Liverpool man having played a considerable chunk of the season in midfield despite being signed as a defensive option.

That does, however, mean that Whelan has the defensive discipline required to replace Guy.

In the 5-3-2 system, it's crucial that at least one of the midfield triumvirate is prepared to sit a little deeper and not leave the defensive players exposed to a counter-attack - particularly if the wing-backs are gong to commit themselves high up the field.

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Guy has performed that role admirably in recent weeks and whoever takes his place in the side will likely have to do similar.

Whelan may just be the perfect option in that regard, but there could be some concerns over his lack of game time in recent weeks.

The 24-year-old has played just 116 minutes since Simpson took charge, with the majority of those coming against Barrow. He was also nursing a swollen foot last week, too.

But having not looked off the pace at Holker Street, Whelan could be a big option.

Danny Devine

News and Star: Danny Devine has frequently featured from the bench under Paul SimpsonDanny Devine has frequently featured from the bench under Paul Simpson

It's been something of a stop-start campaign for the former Bradford City midfielder who has missed chunks of action through injury.

Devine has also yet to start a game under Simpson, although that has likely been due to the good form of Guy rather than anything else.

He has been a regular introduction from the bench though, particularly when United are looking to see out results, and has featured for 91 minutes in total since the new manager's arrival.

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That could well increase in the coming weeks though, with Devine likely to be another leading contender to replace Carlisle's captain.

Similarly to Whelan, he will have the required defensive discipline and has played similar roles in the past.

It would be little surprise to see him feature more prominently in the coming weeks.

Jon Mellish

News and Star: Jon Mellish has impressed in Carlisle United's three-man defenceJon Mellish has impressed in Carlisle United's three-man defence

This would no doubt be a controversial option given Mellish's impressive performances in a back three, but it could be a switch that Simpson is considering.

The ex-Gateshead man has, of course, excelled in the midfield during his time with the Cumbrians - albeit in a slightly more attack-minded role than what is required in this instance.

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But given how Carlisle have improved with Mellish in a central back three alongside Morgan Feeney and Dynel Simeu - conceding just four goals in their last six games, compared with 15 in the half a dozen games prior - a return to midfield would pose something of a risk.

Joe Riley

News and Star: Could Joe Riley be another option for Paul Simpson?Could Joe Riley be another option for Paul Simpson?

An outside option, but one which may be on the table given that Riley has regularly played in a midfield three before.

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But similarly to Mellish, he has impressed in another role since Simpson's arrival and the Carlisle boss may be loath to remove the former Manchester United youngster from the right flank - particularly given that the absences of Kelvin Mellor and Joel Senior leave options on that side of the field limited at present.

So while there is little doubt that Riley has the defensive discipline and ability to fill the gap left by Guy, it seems an unlikely option at present.