Charlton Athletic open their Championship campaign with a narrow but discernible advantage in pre-season momentum, posting a weighted form score of 5.1 out of 10 against Portsmouth's 4.6. That half-point gap reflects steady rather than spectacular preparation from the hosts, who collected 3 wins, 1 draw and 1 defeat across their five friendlies, scoring 5 and conceding just 3. Clean sheets arrived in 3 of those 5 outings, including a 2-0 win at Colchester and a 1-0 success at Gillingham, suggesting a defensive platform has been laid even if the opposition level was modest. The sole blemish came in a 0-2 reverse at AFC Wimbledon, sandwiched between otherwise tidy performances that yielded goals in 4 of the 5 fixtures. Across the sample Charlton averaged 11.8 shots per game, 4.4 on target, and generated 1 expected goal per outing, numbers that point to controlled build-up rather than cutting-edge threat. Possession sat at 36.2 percent, a figure that will rise against Championship defences, while 3.8 corners per match and a 30 percent clean sheet rate underline a pragmatic, counter-orientated approach. The hosts failed to score in only 10 percent of their sample, a reliability that should translate into the opening weekend.

Portsmouth's pre-season tells a less settled story. One win, two draws and two defeats across five friendlies delivered 5 goals but conceded 8, and crucially the visitors kept 0 clean sheets in that run. A 1-3 loss at Wycombe and a 0-2 defeat at Aldershot Town bracketed a patchy sequence that also included 1-1 draws at Farnborough and Bristol Rovers, neither result carrying the hallmark of a side ready to impose itself in the second tier. The lone victory, 2-1 at Woking, came early in the cycle and has been diluted by the shakier outings that followed. Portsmouth averaged 9.6 shots and 2.8 on target per game, lower volume and lower accuracy than Charlton managed, though their 44 percent possession suggests they will attempt to control tempo when the competitive fixtures begin. Expected goals stood at 1.05 per match, fractionally above their hosts, but without a single clean sheet in five the defensive fragility is the headline concern. Scoring in 4 of 5 matches offers a scoring threat, yet the 8 conceded and a 20 percent clean sheet rate over the sample expose the vulnerability that could define their early-season fortunes.

The recent head to head sequence leans Portsmouth's way on current form but Charlton's way historically. Across the last 10 meetings Charlton have 4 wins to Portsmouth's 3, with 3 draws, and the 3.1 goals per game average signals open, attacking encounters between these sides. Both teams scored in 7 of 10, and 8 of 10 went over 2.5 goals, a pattern that sits uncomfortably alongside Portsmouth's brittle pre-season defence. Of the five most recent fixtures itemised, Portsmouth claimed back-to-back wins in February and December 2025, 1-3 at Charlton and 2-1 at home, yet those results came in a different calendar year and the 2024 contests saw Charlton win 2-0 at home and draw 0-0 in the same fixture, while a 2-2 stalemate at Portsmouth in November 2023 added to the sense that goals flow freely when these teams meet. That historical tendency toward high-scoring affairs may be tested by Charlton's pre-season discipline, but Portsmouth's inability to keep a clean sheet in any warm-up match suggests they remain vulnerable to conceding even against a side generating only 1 expected goal per outing.

The numbers point to a home side whose preparation has been more coherent and whose defensive resilience offers a foundation that Portsmouth have yet to establish. Charlton's 3 clean sheets from 5 friendlies contrast sharply with Portsmouth's 0 from 5, and that gap is amplified by the visitors' 8 goals conceded in the same sample. With both teams scoring in 7 of the last 10 head to head meetings and 8 going over 2.5 goals, the fixture has recent history of entertainment, yet Charlton's steady pre-season form and Portsmouth's patchy defensive record suggest the hosts are better equipped to exploit any early-season uncertainty. The half-point form gap is narrow, but it sits on firmer ground when the clean sheet and goals conceded data are layered in, and that defensive edge may prove the decisive factor when the Championship curtain rises.