Premier League giants Chelsea are keeping tabs on Millwall teenager Christian Mbulu, reports say.

The Lions, currently fifth in League One after a fine run, secured Mbulu’s signature on a one-year professional contract in early August.

Mbulu, a promising defender who has been compared with Manchester United’s Chris Smalling, made the switch from non-league club Brentwood Town last summer.

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The 19-year-old is rated highly by the hierarchy at the Den and has featured heavily at an U21 level.

According to the Sun, reigning Premier League champions are tracking the defender.

A major overhaul in the Blues’ squad is expected this summer with Champions League football virtually ruled out after the club’s dire start to the campaign.

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