OSM engine rules and myths

OSM advice often becomes more confident as it travels further from its source. A forum observation becomes a “hidden coefficient”; a useful rule of thumb becomes a guarantee; a percentage shown for one feature becomes an imaginary increase to every player rating.

This page uses three labels. Confirmed means an OSM staff or official update supports the mechanic. Supported means the logic is useful but the exact engine calculation is unpublished. Unverified means the claim may be testable, but should not be repeated as fact.

OSM moderators confirmed in 2025 that a player can remain in an individual training session and still play the scheduled match. The engine does not automatically replace or bench that player merely because the timer is active.

That supports the practical advice: do not bench a key starter solely because he is training. It does not expose a numerical “0% penalty” coefficient; OSM has not published the underlying performance calculation. The safe statement is that simultaneous training and selection is an intended feature. See the moderator answers in Training players and Spelers in opstelling én training?.

The nationality bonus activates with six or more starters of the same nationality. It is not “exactly six,” and it does not grow merely because the lineup contains seven, eight or ten players from that country.

Regional or linguistic combinations do not count. Portuguese and Brazilian, Spanish and Argentine, or Dutch and Belgian players remain different nationalities because OSM reads the player’s country tag. A January 2026 support response explicitly rejected language-based combinations. The existence and six-player threshold are documented in the original Game Updates announcement and the later nationality clarification. Treat any precise performance percentage cautiously because staff statements about the size of the boost have not always been consistent.

Official event announcements describe the standard Training Camp boost as 25% and event versions as stronger—for example, 40% during Training Camp Mania. That confirms a team-level boost, not a visible “+25” addition to every player.

Do not turn a 25% camp into eleven imaginary rating increases. Training Camp, stadium, nationality, player position, fitness and the opponent all feed a hidden match calculation. OSM has not published a formula that converts the displayed camp percentage into player OVR. The Training Camp Mania announcement is useful evidence for the feature percentage, not a licence to invent the rest of the equation.

There is no documented OSM mechanic that rewards ten consecutive uses of 4-3-3 B with an accumulating chemistry or formation-familiarity multiplier. Switching to a suitable 5-2-3 does not create a known chemistry penalty by itself.

Player morale, fitness, natural positions and the coherence of the new tactic still matter. The practical conclusion is narrow: do not keep the wrong formation merely to protect an imagined repetition bonus.

A five- or six-defender low block wants to retreat, protect space and keep the box crowded. An offside trap asks the same defensive line to step forward together. Combining them creates a structural contradiction before any hidden multiplier is considered.

Offside Trap No is therefore the robust default for 5-4-1, 5-3-2, 5-2-3, 6-3-1 and most Counter Attack systems. Consider Yes only with a proactive three- or four-defender line, fit defenders and a willingness to accept transition risk.

Total squad value includes substitutes, reserves and sale inventory that may never enter the match. A compact 18-player squad can field a better eleven than a 25-player squad with more nominal value.

OSM does not publish the full match-strength equation, so avoid claiming that the engine literally reads one particular homemade average. The reliable decision is to compare the likely goalkeeper, defence, midfield and attack, then account for natural positions, fitness, venue and preparation. Total value is context—not the verdict.

Secret Training is documented and visibly prevents normal opponent intelligence about preparation. We did not find a current official source confirming the stronger claim that it always prevents an opponent from playing Friendlies against your team.

Until that behaviour is reproduced in the current game or documented by OSM, present it as a testable observation—not a hidden rule. Secret Training can also conceal a subsequent Training Camp from the opponent, according to an OSM moderator response in Training camp, but concealment is not the same as a universal Friendlies block.

The claim that the post-match pundit approves every tactic except a referee/tackling mismatch is too absolute. Pundit comments can help identify a possible problem, but player logs do not prove an exclusive trigger inside the engine.

Use the report as one diagnostic signal. Record the referee, tackling choice, cards and commentary over multiple matches before promoting a repeatable pattern. Do not reverse an otherwise coherent tactic because of one generic line of commentary.

The liquidity warning is useful; the claimed 30% sale probability is not an official OSM constant. Keep those two ideas separate.

Suppose a manager buys a player for €70M, hopes to sell for €102.5M and assumes only a 30% chance of that sale before being forced to liquidate at €50M. Under those assumptions:

Expected proceeds = (0.30 × €102.5M) + (0.70 × €50M) = €65.75M
Expected ROI      = (€65.75M − €70M) ÷ €70M = −6.1%

The arithmetic is correct if the inputs are correct. The 30% probability must come from your own dated sales log; it is not a universal engine value. The broader lesson survives: expensive players can consume cash and a transfer slot for too long, so judge elite flips on expected profit per slot-day rather than the attractive best-case margin.

OSM does not ask managers to negotiate weekly wages, contract lengths, agent fees or release clauses. Player acquisition runs through the Transfer List, Scout and the game’s basic negotiation features. Advice imported from Football Manager or career-mode contract systems does not belong in an OSM transfer plan.

Before repeating an “engine secret,” ask four questions:

1. Is there a current official or staff source?
2. Does the source confirm the whole claim or only one part of it?
3. Is a percentage being misrepresented as a player-rating increase or universal probability?
4. Could the claim be tested with a dated, reproducible match or transfer log?

The most useful OSM source is not the one with the most precise-looking number. It is the one that makes the boundary between fact, inference and unknown unmistakable.

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