Clive Brunskill/Getty Images

Chelsea defender Tomas Kalas' unplanned inactivity on loan at Koln should be a talking point among Blues staff during the international break when they evaluate the progress of their 26 loanees.

Is this a red flag foreshadowing Kalas' inability to live up to expectations?

"I'd like to play regularly [at Koln in order] to return to Chelsea even stronger," Kalas said, per Sky Sports. "This will be a great test for me."

Chelsea manager Jose Mourinho, technical director Michael Emenalo and youth development technical coach Eddie Newton likely all nodded in unison believing Kalas would start 30-34 league games for newly promoted Bundesliga club Koln.

Seven games into Koln's season, Kalas has yet to start, played no minutes, warmed the benches three times and has been excluded from the first-team squad four times in league play.

If Chelsea head of player welfare Kevin Campello spoke to Kalas 17 days ago, here is a plausible but made up conversation.

Campello: Tomas, can you please give us an update.

Kalas: I played my first game...

Campello: Congratulations!

Kalas: Yeah, but for the second team.

Starting at centre-back partnering former Spanish youth international Roman Golobart, once an "exciting prospect" for Wigan Athletic, Kalas trudged off the field probably thinking to himself: "Why am I playing for Koln II in the Regionalliga West (German fourth division)?"

Who are the Koln defenders blocking Kalas from the starting XI?

Name Nation Position Age Height Weight Tomas Kalas Czech Republic CB/RB 21 6'1" 168 lbs Miso Brecko Slovenia RB 30 5'11" 150 lbs Dominic Maroh Slovenia CB 27 6'1" 187 lbs Kevin Wimmer Austria CB 21 6'2" 187 lbs Credit: FC-Koeln.de.

Miso Brecko: seasoned veteran who captains Koln. His backup is Pawel Olkowski, a 24-year-old Pole.

seasoned veteran who captains Koln. His backup is Pawel Olkowski, a 24-year-old Pole. Dominic Maroh: Started 33 games as Koln conceded 0.59 goals per game in the 2. Bundesliga last season en route to promotion.

Started 33 games as Koln conceded 0.59 goals per game in the 2. Bundesliga last season en route to promotion. Kevin Wimmer: a potential cash cow for Bundesliga's fifth-best defender, per Kicker Koln. He intercepts the ball well and has routinely pulled off last-ditched blocks. Currently tied as the

What amplifies Kalas' vexing situation is Koln manager Peter Stoger's problem is not defence, it is his attack.

Koln are tied for the third-best defence in the Bundesliga (six goals conceded in seven games), but they have the second-worst attack (four goals scored in seven games).

Signed from Czech club Sigma Olomouc for €6.6/£5.2 million in 2010, Kalas was not the only young gun centre-back in the market.

Palermo bought then-19-year-old Argentine Ezequiel Munoz from Boca Juniors for €5/£3.9 million. He has been steady for Palermo, but has yet to transition into a world-class centre-back.

Rangers received "€2.5/£2 million up front with add-ons linked to games played, taking the total value of the deal to €6.4/£5 million," per Andy Hunter at The Guardian, when then-18-year-old Scotsman Danny Wilson was sold to Liverpool.

Instead of becoming the next Alan Hansen, Wilson played nine games for Liverpool. He is now rebuilding his career with Heart of Midlothian.

Schalke spent €2.5/£2 million on Olympiacos' then Greek 18-year-old Kyriakos Papadopoulos.

Question marks over his long-term durability have hindered him from fulfilling his potential. He is currently on loan at Bayer Leverkusen.

The reprieve for Chelsea should Kalas turn into another Jeffrey Bruma is none of the transferred centre-back prospects of 2010 have emulated Raphael Varane's rise to the top (Real Madrid signed him from Lens for €10/£7.9 million in 2011).

After two seasons as a starter on loan at Vitesse, Kalas has regressed post-leg break.

"[As a 17-year-old] I was happy just to work with the [Chelsea] first team to make up the numbers," Kalas said, per Dominic Fifield at The Observer (h/t The Guardian). "[Now] I'm just desperate to play games, like I did at Vitesse."

When asked about his Chelsea career, Kalas once joked: "I am a player for training sessions. If they need a cone, they put me there."

That has become a stark reality on loan at Koln.

@allanjianga

+allanjiang

Statistics via WhoScored