I’ll echo what @TrainForPain said: as an athlete, “bulking” up should not be in your language.
That’s not to say that you shouldn’t build muscle. But muscle lost during the season (happens to most athletes in most sports) is quickly regained when you resume a normal lifting regimen.
In fact, guys like Poliquin used to use that rebound phenomenon to claim massive body comp gains in minimal time with athletes…
For example, a hockey player might lose 5kg of muscle and gain 3kg of fat in the season. (NHL players are always on the road and eat at restaurants a lot, not always clean food. Most get fatter during the season).
When they begin their off-season training they put back the lost muscle in less than 4 weeks and by starting to eat properly they lose the fat.
Then the coach can claim that his methods had the athlete gain 5kg of muscle and lost 4% body fat in 4 weeks 
I’ll tell you three stories to illustrate the good and bad ways to do this.
1st STORY
The first one is about myself.
My first year of college football I was 85kg as a linebacker. Most linebackers on the team where 95-105kg as a result I did not see any playing time that season.
So I decided to bulk up the next off-season to come in much heavier. I ate like maniac, mostly crappy food just to get in the calories. I used a formulation called “The Get Big Drink” from an article by John McCallum which was essentially a 3000 calories drink that you drink during the day on top of you meals.
Come training camp I was massive (well for me at the time). 102kg (on 175cm). I was also much stronger, with a 230kg/500lbs squat (to parallel back then, not ATG).
My coaches were super happy and I got the starting job as a middle linebacker…
Job that I lost a week later because I was just too damn slow on the field and didn’t see playing time after that!
2nd STORY
This one is about a pro football player I trained.
He was a 95kg linebacker (185cm), who mostly played special teams. He contacted me after seeing a bobsleigh guy I coached, train.
The program I gave him was strictly performance-based. Using my Omni-contraction system. He actually complained about the lack of hypertrophy work as he needed to add mass.
After the off-season he ended up at 105kg but he was actually faster because he did not gain any fat.
3rd STORY
I was training this college football player. Middle linebacker (there seems to be a trend) he was a dominant player because he had great instinct.
But he wasn’t really fast. His reaction time just made his game speed much faster than his real speed.
He was also very strong.
The problem was that he wasn’t big. He was 91kg on 180cm. Now, he played CANADIAN college football which has different rules than US college football (larger field, 12 players instead of 11, 3 downs instead of 4). The Canadian game is a lot more pass-dominant so typically linebackers aren’t as big in the US as they are essentially big safeties.
Anyway, his school hired a new coaching staff… who were coming from US college football.
And they had the US mentality that a linebacker is mostly a run stopper and need to be at least 100-105kg.
My athlete got told that if he didn’t weight at least 100kg, he would lose his starting job.
Now, the problem is that he could not afford to weigh 100kg, he was already slow. If he got any slower his reaction time and game understanding would not be enough to mask his lack of speed.
So he asked me what to do…
I told him: “We will train like we always do. You’ll come to camp and dominate the physical tests and when they do the weight-in, wear baggy shorts an put weights in your pockets”
That last part was a joke… or so I thought.
Anyway, a few months later he is in camp and calls me up.
“It worked!” he told me.
“What worked?”
“The weights in my pockets!”
Anyway, he indeed got the highest squat and bench tests, got his starting job, and made the all-stars team.
THE MORAL OF THE STORY
Is that don’t worry about the number on the scale. It doesn’t matter.
Train to become stronger, more powerful and mostly, FASTER.
The body you end up with after that is the body that you need to be the best version of “football playing you” as you can.
As for the injuries, I’m honestly sorry, it’s no my lane.
MY OLD COACH USED TO SAY…
“You are much more likely to come up one yard short than one kilo short”
In other words, speed and agility is what matters. Not weight.