Neil Harris exceeded all expectations with Millwall, but he will have a tough task to replicate these achievements.

Millwall have a small squad, but are likely to have ambitious aims next season after a strong first season back in the Championship. Therefore, new signings will be necessary as well as moving on players who aren't good enough.

This season in the Championship should give some significant funds to improve the squad because Harris had a tiny budget to make adjustments with last summer. Therefore, they can afford to go after bigger targets.

Here are four pieces of business that need to happen...

Martin was signed last summer to act as back-up for Jordan Archer and he did that with just one league appearance. He was brought in on a short-term contract, but that was extended to last until the end of the season. It was then extended for another season in March.

However, this could have just been a safety option in order to ensure they have back-up in case they are unable to bring in someone else. If they are able to bring in a better alternative or someone who can provide serious competition for the role then they should consider selling Martin or loaning him out for the rest of his contract.

Grant is an experienced veteran who would be the ideal back-up for Archer in the upcoming season. He was recently relegated with Stoke City, so he's probably going to need a new club, but his age means he isn't likely to be a starter for most clubs.

Therefore, adding him would be more useful behind the scenes because of his experience and potential leadership. Moves like these are useful for sides that require a little bit more to achieve their targets such as John Terry moving to Aston Villa. Having another reasoned voice in the dressing rooms helps in key moments.

O'Brien made 30 appearances with 23 of them being starts, but he only scored four times and assisted once. Ben Marshall contributed more in less time even though he had to adjust to the club because he came on loan.

The 24-year-old did miss a couple of months due to an ankle injury, but they should consider selling him if they want to continue progressing as a club because he isn't up to the level they need.

Grosicki would fit into Millwall's style because he is a traditional winger, so he would thrive in the requirements at Millwall because he could keep providing service to the strikers without having to do anything too complicated due to the simplistic style that is utilised by the team.

He scored nine goals and assisted five in 37 league appearances for Hull, so he is certainly good enough for the Championship. His age means the fee shouldn't be too large either because he will be 30 by the time the season comes around, so he would be a good piece of business.