IM

Koellner, Ruben Gideon

GER GER·Born 2004·FIDE #12993093·2,597 Games

Classical25062,513 Games
Rapid242543 Games
Blitz238441 Games

Statistics

2597

Total

1151

Wins

483

Draws

957

Losses

44%19%37%

Play Style

What you need to know before facing them

Elite accuracy: 93.2% average
High resilience (62%): Dangerous even when losing
Solid conversion: 89%
Very consistent (88%)
Very precise: only 0.1 blunders/game
Dominates 1.Nf3 ♔ (75% in 16 games)
Vulnerable to 1.Nf3 ♚ (only 37%)

Deep Analysis

Stockfish 18 · Classical games · 527 analyzed

Accuracy by phase
Opening95.7%
Middlegame93.4%
Endgame95.7%

Clutch Factor

Performance under pressure

+5%
Winning (+2 or more)94%
239 Games
Equal position94%
167 Games
Losing (-2 or more)89%
94 Games

Problematic Pieces

Which pieces cause most errors?

♖
23%
87 errors
♙
22%
82 errors
♕
16%
61 errors
♞
14%
51 errors
♗
13%
48 errors
♔
12%
46 errors

Critical Moment

When does the first serious error occur?

Move 41average
1-15
16-25
26-35
36-45
46+
38% of blunders occur between move 46+. Keep tension until that moment.

Error Heatmap

Where do most errors occur?

12
11
15
14
10
12
14
13
13
14
abcdefgh
Many
Few
Critical squares
e515 err
f314 err
f414 err
f514 err
c313 err
e5/f3 concentrate most errors. Force decisions in those zones.

Recent Games

D
Karthik Venkataraman2594

grenke Chess Open 2026 · 6 Apr 2026

½-½
D
Karthik V2028

grenke Chess Open 2026 · 6 Apr 2026

½-½
W
Abdurakhmonov, Mukhammadali2339

grenke Chess Open 2026 · 6 Apr 2026

1-0
D
Willems, Niels2388

grenke Chess Open 2026 · 5 Apr 2026

½-½
W
Kalogridis, Antonios2386

grenke Chess Open 2026 · 5 Apr 2026

0-1
D
Hong, Andrew2598

grenke Chess Open 2026 · 4 Apr 2026

½-½

Openings

Based on player games

Weaknesses

EXPLOIT!
White

No significant weaknesses detected as White

Black
Reti: Double Fianchetto
72.2%
18 Games·Loses

1.Nf3 Nf6 2.g3 d5

King's Indian
52.9%
17 Games·Loses

1.Nf3 d6 2.d4 Nf6 3.c4 g6

Strengths

AVOID
White

No consistent strengths detected as White

Black
Ruy Lopez: Morphy
45.5%
22 Games·Wins

1.e4 e5 2.Nf3 Nc6 3.Bb5 a6

Critical Blunders

Tactical errors analyzed with Stockfish

10 errors
▶
#29Rf8??
Tactics
vs Vogel
Rapid·2025
▶
#35Rc7+??
Tactics
vs Wagner
Rapid·2025
▶
#9Bc4??
Tactics
vs Santos Latasa
Rapid·2025
▶
#14Qe6??
Tactics
vs Rodshtein
Blitz·2025
▶
#51Kd6??
Endgame
vs Teclaf
Rapid·2025
▶
#23Rxb6??
Tactics
vs Sarana
Rapid·2025
▶
#35Qc5??
Tactics
vs Hansen
Rapid·2025
▶
#22Nb3??
Tactics
vs Kozul
Blitz·2025
▶
#23Ra5??
Tactics
vs Gumularz
OTB·2024
▶
#31bxc6??
Tactics
vs Dominguez Perez
OTB·2024
Endgame Statistics

23 endgame categories analyzed — discover where they collapse under pressure

Repertoire
☰ All
♟ Classical
⚡ Rapid
🔥 Blitz
PRO
·
2026
2025
2024
2023
2022
2021
PRO
8
7
6
5
4
3
2
1a
b
c
d
e
f
g
h
Starting Position
1302 Games
48%18%34%
1.d4
57%
1264
1.e4
65%
17
1.Nf3
75%
16
1.c4
0%
1
1.d3
100%
1
1.h4
100%
1
1.a3
100%
1
1.c3
0%
1
chessstalkerv3.5

Know your enemy. Win more games.

Resources

Trust & Privacy

🍪No tracking cookies
🔒SSL encrypted
📊Self-hosted analytics

© 2025-2026 Chess Stalker. Not affiliated with Lichess.org or Chess.com

Made with ♟ for chess players

🍪 Cookies · Chess Stalker uses technical cookies (required for operation) and analytical cookies (to improve the service). Analytical cookies are optional.