Two days before the 49ers full squad reports, the fates of tight end Vernon Davis and guard Alex Boone remain undetermined. Both are expected to hold out.

As has already been mentioned, the 6-8, 300-pound Boone has drastically out-played his contract. If he realizes his $200,000 roster bonus, he will make $2.2 million this year, less than half what he should be making.

The issue with Boone is re-doing his deal without impacting the team’s salary cap. The 49ers are only $5.9 million under the cap, and once the team sets its final roster in September, some roster bonus money will be due. That will likely gobble another one or two million more of cap space.

Every team likes some cushion under the cap if they need to sign players during the season.

Since Boone makes so little, it would be difficult to provide him with a sizable signing bonus and still maintain a prudent cap reserve. However, the Colin Kaepernick and Joe Staley extensions provide a way out.

Both those contracts were based partially on game day roster bonuses, which is the 49ers’ preferred way of doing business. Kaepernick will earn $125,000 in roster bonuses for being on the active roster during most of his six-year contract. Staley gets $500,000 a game for being active in 2015.

The 49ers also like to attach more incentives to team and individual performances such as Super Bowl appearances and All-Pro designations. However, most players want abundant cash just by signing their names (signing bonus). For many reasons, that’s unlikely to happen in Boone’s case.

Meanwhile, Davis’ holdout is simply a bad move on his part. Davis is now playing out a contract that guaranteed him $23 million. His contract average of $7.35 million is the third-highest in the league for a tight end.

A holdout would not only incur fines of up to $30,000 a day, but holding out into the season could cost Davis some of his $406,250 in roster bonus cash.

Unfortunately for Davis, his contract is front-loaded, meaning that he has combined $9.050 million left in salary over the next two years. Davis is also fighting the age factor; he is now 30.

The only way out for Davis is again to sign a cap neutral extension that pushes much of his new earnings into game day roster bonuses. The 49ers might interested in offering such a deal.