Chris Smalling Blow Adds More Defensive Instability Manchester United Don't Need

Manchester United are in a period of transition. It's only natural they're still reeling—more than a year on— from Sir Alex Ferguson's retirement. In terms of managerial changes, it was a seismic shift.

Louis van Gaal's job, one of them at least, is to bring stability back to a club that has seen very little over the last 12 months. It should have started on September 2, when the transfer window finally shut.

Instead, however, United have appeared stuck in a constant state of flux. And no more so than at the back.

When Jonny Evans, Marcos Rojo and Michael Carrick were thrown together as a back three in the 39th minute at St Mary's on Monday night, they became Van Gaal's 18th centre-back combination in the Premier League this season.

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It would be an incredible stat if it had been across an entire season. It's even more so when you consider they have only played 15 games. 

In contrast, Jose Mourinho has been able to pick Gary Cahill and John Terry in every Premier League game this season. It's no coincidence that Chelsea are three points clear at the top with the second-best defensive record in the league.

Van Gaal has used 10 players at centre-half, including two midfielders, Daley Blind and Carrick. Three young players—Tyler Blackett, Paddy McNair and Tom Thorpe—have been given their senior debuts. He's started with a three-man defence five times and a four-man defence 10 times.

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Phil Jones, Chris Smalling, Evans, Rojo and McNair have all spent time on the sidelines through injury. Smalling and Blackett have served suspensions. Michael Keane, who came on as a substitute against Sunderland in August, is now on loan at Burnley.

Smalling is the latest injury victim after he limped off in the first half against Southampton. As reported by the Manchester Evening News, he is set to miss two weeks with a groin injury, ruling him out of the games against Liverpool at home and away to Aston Villa. It is especially disappointing for Smalling, who has been impressive since his red card against Manchester City.

Statistically, Smalling and Rojo have been United's most reliable partnership. They've started together four times in a back four, conceding twice in 309 minutes, a goal every 155 minutes. 

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It's not a bad record. But they won't be reunited against Liverpool at Old Trafford on Sunday because of Smalling's latest set-back. We could yet see combination No. 19.

Van Gaal hasn't been afraid to chop and change this season. But he wouldn't have envisaged making this many alterations to a part of the team that usually relies on consistency. In the circumstances, it's an even bigger achievement that they're third in the table.

Yet, there is still a feeling that the lack of stability is holding United back. That, with the benefit of a settled team, they would be further along in their development under Van Gaal.

They have had to deal with a lot of change over the last 12 months. Unfortunately for the new manager, it shows no sign of stopping.