Adrian Clarke looks at key tactical points ahead of Matchweek 29.
The Spaniard has scored three goals in his last two Premier League outings and has exerted a remarkable influence on the team this term.
Frank Lampard's side have won seven of the eight top-flight matches Alonso has started, scoring more goals and conceding fewer.
|2019/20||Alonso starts||Alonso not starting|
|Goal diff.||F22 A8||F25 A31|
Given the remarkable statistics above, the 29-year-old is surely in line to start again at home against Everton this Sunday.
Lampard has missed the adventure that Alonso provides down the left side for much of this campaign, especially at Stamford Bridge.
The only dilemma for Chelsea's head coach will be which formation to fit Alonso into.
Lampard's preference appears to be a traditional four-man defence but Chelsea have been more reliable with a back three.
They have only lost one Premier League match in a 3-4-2-1 system this season, a 2-0 home defeat by Southampton.
|Premier League||Matches||Pts||Ave. pts|
It frees up room for an extra attacking midfielder to be selected, instead of a defender.
However, the quality of the Blues' attacking full-backs means they can switch seamlessly to 3-4-2-1.
They create chances, deliver end product and take up extremely advanced positions.
As natural wing-backs, they are ideally suited to Lampard's plan B.
|Marcos Alonso||1.99||Trent Alexander-Arnold||2.67|
|Jeffrey Schlupp||1.47||Lucas Digne||2.42|
|Matt Doherty||1.31||Marcos Alonso||1.76|
|Touches in opp. box||Open-play crosses|
|Marcos Alonso||4.33||Trent Alexander-Arnold||6.73|
|Matt Doherty||3.32||Benjamin Mendy||5.47|
|Cesar Azpilicueta||3.10||Reece James||5.47|
In the short-term at least, Alonso's knack for finding goalscoring positions makes him invaluable.
Another advantage Chelsea have when using three centre-backs is the extra height it gives them when defending set-pieces and crosses.
This has been an area of weakness throughout Lampard's first season in charge at Stamford Bridge.
|Headed goals||Goals from corners|
So despite beating Liverpool 2-0 in the FA Cup this week with a back four, it may be prudent for Lampard to consider reverting to a back three.
Bringing in an extra centre-back, while releasing Alonso and James to play further forward, could pay off against the Toffees.